Sion Build Guide by Stinkee

I have been a Sion main since his rework. I have obtained over 800,000 Mastery Points on Sion across my accounts. In Season 6 I reached Diamond with a 68% winrate on Sion over 169 games. He has been my favorite champion in League since his rework.

Sion is THE most versatile tank is League of Legends. He is able to adapt to each game unlike no other tank. Many people even play Sion as an AD assassin or bruiser including Thebausffs and Tilterella both Challenger AD Sion mains and streamers. He is always going to be a great tank who can fill the role that is needed for his team. Sion is very easy to learn but also has the highest skill-cap of any tank in the game, making him a both a great champion for new players and for masters alike. I suggest you use this guide as a foundation to find your own way to play that works for you. Don't strictly follow everything in the guide, decide what works best for you and how you play best. There's no one "right" way to play or build this champion and you'll find that most high elo Sion players have drastically different play-styles and builds.

P Glory in Death Innate: After being killed, Sion will reanimate with rapidly decaying Health. His attacks become very rapid, gaining 100% Lifesteal and deals bonus damage equal to [+10% target's max] All his abilities are replaced with Death Surge.png Death Surge, which grants a burst of Movement Speed.

Q Decimating Smash Active: Sion charges up a heavy blow for up to 2 seconds. When released, he deals physical damage to enemies hit (60% damage to minions) based on how long Sion charges and briefly slows them. If Sion charges for at least 1 second, enemies are knocked up and stunned for 1.25 to 2.25 seconds.

W Soul Furnace Passive: Sion gains 4 maximum Health whenever he kills a unit (15 for champion kills, assists, large minions and large monsters). Active: Sion shields himself for 6 seconds. After 3 seconds, while the shield holds, Sion can reactivate to deal magic damage to nearby enemies. Max 400 bonus damage against minions and monsters.

E Roar of the Slayer Active: Sion fires a shockwave, dealing magic damage to the first enemy hit and knocking it back if it is not a champion (significantly increasing its range). Target's hit by the shockwave or the knocked back unit take the same damage and are slowed for 2.5 seconds and have their Armor reduced by 20% for 4 seconds.

R Unstoppable Onslaught Active: Sion charges in a direction for 8 seconds and can steer slowly towards the mouse cursor. While charging, Sion is immune to all Crowd Control. Reactivating will cancel Sion's charge early. When Sion collides with an enemy champion or wall, he deals physical damage and knocks up enemies in a small area for 0.75 seconds. Enemies in a larger area take the same damage and are slowed for 3 seconds. The damage increases and the stun duration increases to 1.75 seconds as Sion charges further.

Eternals were added to the game in patch 10.5. They are a (paid) way to track achievements for a specific champion. Sion currently has 3 unique Eternals.

Smash'em Up Tracks total enemies knocked up by Decimating Smash Well Fed Tracks bonus health gained from Sion's Soul Furnace passive The Pain Train Tracks the total number of enemies that you hit with Sion's maximum speed (950 movement speed) ult Unstoppable Onslaught

View the Sion Matchups section under the "Tank Sion Top or Mid" build. Currently most matchups are focused on top and mid lane. Click "Show All" under the picture of Sion in the Threats & Synergies area to expand and see everything.

General Rule for Counters and Synergies

Counters: In general, Sion is countered by high mobility, %hp damage, hard CC/skillshots, and bruisers. Every one of Sion's abilities are very telegraphed, making them very easy to dodge by champions with high mobility. Sion is a health stacking tank, making %hp very effective against him. Hard CC and skillshots are very effective against Sion because he has to charge up his Q, making him a vulnerable target. Bruisers as a class in general are designed to do well against tanks, they do higher damage than tanks, usually have some form of %hp damage or armor shred, as well as having higher mobility at the cost of having less CC and defensive abilities than a tank.

Synergies: Since Sion has very telegraphed but hard hitting abilities, he pairs very well with other champions that have easier to land/setup CC. Sion's ult and Q are much easier to land on targets that are already CC'd. Champions like Nautilus with a ton of CC makes your job as Sion much, much easier. Also, Sion is a great setup for other champions, such as Yasuo that need enemies to be CC'd for them, although Sion is not the best at this because his abilities are so telegraphed. Keep in mind, that too much CC on a team is a bad thing and makes items like Mercury's Treads and Quicksilver Sash more valuable.

Resolve Tree

Grasp of the Undying is great on Sion. It does damage based on your max health, heals you, and gives you permanent health every time you proc it.

Demolish is another great rune for Sion. It also scales with your health allowing you to kill towers very fast as a tank! Shield Bash can be good on Sion as well for better trades in the top lane. If you want better trades in lane and massive shield damage late game take Shield Bash. If you think you can win your lane hard and hit the enemy tower for free often take Demolish.

Conditioning, Second Wind, and Bone Plating are all equally good on Sion and are completely situational. Conditioning is the best option outside of laning phase, if you are against an easy lane take it. Second Wind is good against poke lanes. Bone Plating is the based overall rune in this tier for trading, making it the best overall option in most situations. If you are unsure what to take in this tier just take Bone Plating.

Overgrowth is the best rune option in the bottom tier of the Resolve tree. It gives you permanent health when minions die near you. Sion is a health tank so this is always a great option on him. If you need help in the laning phase you can take Revitalize which will increase your shield strength. If the enemy has a ton of CC, think about taking Unflinching instead as it will help you deal with the CC.

Sorcery Tree

Arcane Comet Is a fantastic rune on Sion for the laning phase. Sion's Q Decimating Smash and his E Roar of the Slayer basically guarantee the comet to hit. This gives a Tank Champion like Sion insane poke in the laning phase, allowing him to deal with ranged matchups and easily beat them. If you go Arcane Comet start Doran's Ring and max his E Roar of the Slayer.

If you took Comet I'd recommend taking Manaflow Band as well, giving Sion the mana to be able to spam his e nonstop in the laning phase.

Transcendence should be taken next, giving Sion an easy 10% extra CDR.

Scorch is very good in this rune page. It increases Sion's poke damage by a lot.

Inspiration Tree

Glacial Augment is a good rune to take if your team needs more engage. It also makes Sion's Q Decimating Smash a lot easier to land. If you go Glacial Augment buy Turbo Chemtank second or third item allowing you to run very fast into the enemy team and slow them with the freezing rays from Glacial Augment. Prototype: Omnistone is another viable option for Sion top. I would only ever take it against ranged matchups such as Kennen and Teemo. The reason this rune is viable vs. ranged top laners is because Grasp is not useful against ranged top laners and the ability to cycle between keystone runes is very useful. This keystone on Sion top at the 2020 world's vs. a Kennen top. Unsealed Spellbook is good for the same reasons that Prototype: Omnistone is good. It allows you to have more utility and options against a ranged top/mid. Unsealed Spellbook is a great rune but it has a VERY high skillcap.

Magical Footwear and Perfect Timing are both solid options to take next. Magical Footwear is good if you don't need to buy Ninja Tabi early. Perfect Timing is good if you think the enemies will dive you top lane. Keep in mind, both of these runes take a while to activate.

NERFED 9.16 Biscuit Delivery may not be viable to take every single game now. It should still work in difficult matchups but may not be ideal otherwise. If Inspiration is your secondary tree I would try taking Magical Footwear instead. If Inspiration is your primary tree I would still take Biscuit Delivery in most situations.

Cosmic Insight, Approach Velocity, and Time Warp Tonic are all good runes at the bottom of the Inspiration Tree. I prefer Approach Velocity, it gives you movement speed when you run towards enemies that you CC. This is great on Sion because if you land Roar of the Slayer you will be able to catch up to them and use Decimating Smash. This also makes for an amazing synergy with Glacial Augment and Sion's Passive Glory in Death allowing you to chase people way easier.

Starting Items

For Sion's first purchase you can decide to go Corrupting Potion, Doran's Shield + Health Potion, or Doran's Ring + Health Potion x2. Corrupting Potion is great in every scenario and works with any build. It provides amazing sustain and damage for the laning phase. If you are new to Sion I would always recommend starting Corrupting Potion. Use Corrupting Potion offensively to win trades. Doran's Shield is a great start against poke and ranged champions. It will reduce their poke by a ton but also gives you no mana sustain so watch your mana when taking Doran's Shield. Doran's Ring is a good start if you want to poke the enemy. This will increase your E Roar of the Slayer damage by a large amount and allow you to spam it much more. Buying Doran's Ring will force your Adaptive Force to give you AP instead of AD. Starting Doran's Ring will give Sion's E Roar of the Slayer +18 damage at level one and Sion's W Soul Furnace +13 damage at level one while also increasing Arcane Comet damage if you took it. This will increase your ability to poke by a large margin, making Doran's Ring a great start against ranged matchups that you want to poke down. Look to spam E Roar of the Slayer and if it lands charge your shield and channel Q.

Boots

Sion can go either Plated Steelcaps or Mercury's Treads depending on each game. Look at the enemy team and your laner. If you are against a heavy AD team go Plated Steelcaps, if you are against a heavy AP or heavy CC team go Mercury's Treads. In most cases you will probably end up buying boots early to counter your laner. If you're against a heavy auto-attacker like Tryndamere, you'll want to get Plated Steelcaps very early to reduce the damage of his basic attacks.

MYTHIC ITEMS

Sunfire Aegis: Sunfire Aegis is an improved Sunfire Cape from the previous seasons. This is the default DAMAGE choice for tanks. If you do not care for utility and just want to do a lot of damage and be a constant threat then this is the choice for you. The main issue with this item for Sion is that it takes a while to ramp up. Sion generally has shorter trades and blows his cooldowns at the start of the fight while having a hard time sticking to enemies, so having a ramping damage item is not ideal for him. This item also gives all Legendary Items +5 ability haste, allowing Sion to spam his abilities more. Keep in mind that Riot intentionally made this item less cost effective because they wanted tanks to be able to viably buy any of the 3 tank mythic items

Frostfire Gauntlet: Frostfire Gauntlet is an improved Iceborn Gauntlet from the previous seasons. This item has a weaker version of the Sunfire passive. This is a solid utility and brawling choice for Sion. The slowing field is large and is great for setting up Sion's Q - Decimating Smash. If there are a lot of mobile champs on the enemy team or you just want to be able to stick to them and have an easier time landing your Q, this is a solid choice. This item also gives all Legendary Items +100 health and +7.5% champion size so you will be HUGE. Frostfire Gauntlet also gives more armor and less magic resist than the other mythic items so if you need more armor, this is a good choice

Turbo Chemtank: Turbo Chemtank is an improved Righteous Glory from the previous seasons. This item has a weaker version of the Sunfire passive. Turbo Chemtank is the best teamfight and engage mythic tank item. Chemtank will be a great option if you are the primary engage on your team and need a more reliable way to engage in teamfights. It is also pretty solid for peeling for your carries. Turbo Chemtank also gives all Legendary Items 5% tenacity and slow resist so it is also great against heavy CC teams. This item synergizes extremely well with the Glacial Augment keystone rune!

LEGENDARY ITEMS

Thornmail: Thornmail is the default anti-healing tank item. ALWAYS get this item or just Bramble Vest if there is a good amount of healing on the enemy team.

Randuin's Omen: Randuin's Omen is the anti-crit and anti-auto attacker item. Great against crit adcs and top laners such as Tryndamere, Quinn, Gangplank, etc. The active is also very nice in teamfights, slowing all nearby enemies as well as their attack speed.

Frozen Heart: Frozen Heart is similar to Randuin's Omen in the way it is good against auto-attackers. Frozen Heart is better than Randuin's Omen against on-hit auto-attackers like Vayne, Kog'Maw, Irelia, etc. and worse against crit auto-attackers like most ADCs and top laners like Tryndamere. Frozen Heart is also now the ONLY tank item that gives mana, so if you need mana, this is the best item for you. Frozen Heart also gives more Ability Haste (aka CDR) than any other tank item.

Gargoyle Stoneplate: Gargoyle Stoneplate has been reworked and is the best hybrid (armor + magic resist) tank item. The active gives you a shield based on BONUS HEALTH which is REALLY good on Sion because of his W - Soul Furnace passive. This item is the ultimate teamfight tankiness Legendary Item. If you want to survive in teamfights this is the best item for you IF the enemy team has fairly balanced physical and magic damage.

Titanic Hydra: Titanic Hydra is a great item if you are fed and just want to do a ton of damage. It no longer has an active but does really solid cleave damage based on your MAX health. Titanic Hydra, paired with Sunfire Aegis gives you a lot of damage for a tank.

Death's Dance: Death's Dance was given a small rework with the item changes in preseason. It is now an anti-ad item item only. That being said, it is REALLY good against ad champions. Death's Dance will likely be a very solid late game item choice on tank or bruiser Sion, especially to counter burst ad champs like assassins.

Spirit Visage: Spirit Visage is a solid Magic Resist choice. It now increases your healing AND shielding by 25% which will increase your W - Soul Furnace shield size by a significant amount as well as the Gargoyle Stoneplate and Sterak's Gage shields if you get either or both of those items.

Force of Nature: Force of Nature is another great Magic Resist choice if you are having trouble sticking onto the enemies. This item will give you a lot of movespeed and magic resist (ramping up when you are getting attacked). Force of Nature is really great against DOT mages because it will stack the passive much faster than other champions.

Abyssal Mask: Abyssal Mask is again, a really solid Magic Resist option. It was reworked and now, when you CC an enemy they will take 10% increased damage from ALL sources for 4 seconds. This is item is amazing for teamfights and will buff your teammates by a large amount. 10% damage increase on anyone that you Immobilize (Q stun or R) is huge for teamfights.

Warmog's Armor: Warmog's Armor is relatively unchanged in the preseason and is still a great option on Sion if you want the sustain and health. This is a great item if you need to match a splitpushing threat, allowing you to take short trades then heal up and stay in lane forever.

Sterak's Gage: Sterak's Gage is a solid damage/bruiser Sion item. It now gives you health regen when getting attacked OR attacking an enemy, based on your max health. It still has the shield against burst.

Knight's Vow: Knight's Vow is a great mid or late game to support a fed carry. If your ADC/mid/Graves, Yi jg/etc is your win condition and your team does not already have a Knight's Vow, just buy this item and peel for them, it will win you the game.

Zeke's Convergence: Zeke's Convergence is another great mid or late game support item. It is similar to Knight's Vow but instead of protecting your carry, it will give them more damage when you CC enemies. I think this item is OKAY if you want to buff your super fed carries late game but it's not nearly as good as Knight's Vow for your team. I would only buy this item if your carry teammate is your team's win condition AND you already have Knight's Vow for them.

There are some great Sion mains to watch to get better at Sion. Thebausffs is an EUW Sion one trick who is consistently in high Challenger by playing AD Sion and occasionally tank (bruiser) Sion. He is THE master of this champion. He streams on Twitch very consistently and has a Youtube channel. He just released a very in-depth Sion guide which I highly recommend you watch if you want to get better at Sion. Tilterella is also a great Sion main to watch. He has a Youtube channel with over 350k subscribers and most of his content is related to Sion. He also has a Twitch stream. He plays on the OCE server and has managed to get very high elo including Challenger in the past.

Tank Sion

Building tank on Sion is the most common and well-known way to play Sion. It is highly recommended for new players to try tank Sion first to learn the kit. Tank Sion is easy to learn but hard to master. Building tank on Sion insures that even if you have a hard time in lane you can still be useful by engaging or peeling for your carries.

Top Tank

Top lane is the obvious choice for tank Sion. Sion works top because he can survive the laning phase and generally, tanks want to be picked into the top lane. He still has such very rough matchups like Darius, but in general Sion top will do fine.

Mid Tank

Sion mid is actually not bad. Many people have played it in the past, even Faker has played Sion mid. I would only recommend doing this if your top laner is a carry and your team absolutely needs a tank. Also insure your team has enough magic damage before locking in Sion mid. Going mid as Sion allows you to roam a lot more than you would as a top laner. Sion mid can absolutely destroy many mid matchups. Picking Sion into a Zed mid, for example is an easy way to make a Zed ragequit. Sion, unlike other tanks does really well against ranged matchups so you can do really well against many mid laners. Look to build a large waves and crash it into the enemy tower then roam top or bot. Your ult is really good for roams. As soon as you hit level 6 you can try to roam bot and make an ult play as the enemy bot laners will likely only be level 4 or 5.

AD Sion

AD Sion is an incredibly fun and viable way to play Sion. Building lethality on Sion essentially turns him into an assassin. Sion's Q Decimating Smash has ridiculous AD scaling, allowing you to almost one shot enemies if you can get a full Q off. If your Q Decimating Smash doesn't kill them, they will be cc'd for a long time allowing you to use your other abilities to finish them off. While playing AD Sion you are going to want to camp in bushes a lot. Enemies CANNOT see when you are channeling your Q Decimating Smash from a bush UNLESS the bush is warded. This allows you to pull of some sneaky oneshots from bushes. Even when you die as AD Sion you will run down the enemies with your passive, possibly taking one or more enemies with you. I don't main AD Sion but I love to play it sometimes on my smurf, it is incredibly fun to play. Several Sion mains have managed to reach Challenger one tricking AD Sion.

Support Sion

Support Sion is a viable pick but is not as popular as his other roles. While not many people play Support Sion, it can be quite good. Sion as a support is very aggressive, all of his abilities can potentially hit both enemy bot laners. Make use of the bot lane bushes to charge your Q Decimating Smash on the enemy both lane, they cannot see you charging it if the bush is not warded. He will not be as tanky as he would be top lane so you need to be more careful. Try to pair with an aggressive ADC and stomp the early game. Try to peel for your ADC lategame, don't ult too far away from the carries or they might die alone. If you secure an early lead use your lead to get vision in the enemy jungle and near dragon. You should not lose a single dragon early game if you win hard bot lane. Make sure dragon is always clear of wards and use wards in the enemy jungle to spot where the jungler is going. You can max either E Roar of the Slayer or Q Decimating Smash on Support Sion. Q Decimating Smash max is good if the enemy bot lane has low mobility and can easily get hit by Q. E Roar of the Slayer is good to max first against poke lanes and more mobile lanes. As Support Sion ALWAYS max W Soul Furnace second.

Jungle Sion

Sion jungle has been buffed in patches 9.16 and 10.20. His Q Decimating Smash no longer does reduced damage to monsters and its base damage has been increased in the 9.16 patch. In the 10.20 patch his Q now does 150% damage to monsters, this is HUGE for jungle Sion and also decent for lane Sion. Sion Q, fully charged could potentially outdamage a smite now! These changes made Sion jungle viable again, improving his clear speed by a large amount. Sion's weaknesses in the jungle will still remain, he will still not clear as fast as many junglers and his pre-6 ganks are not ideal without Predator. Sion jungle does scale much better than top lane Sion though. Sion's W - Soul Furnace passive stacks faster in the jungle than in top lane because you get extra stacks from large monsters. This rewards Sion for playing a farm-heavy jungle style.

Bruiser Sion Top

Bruiser Sion is very similar to tank Sion. The main difference is in which second item you buy. Bruiser Sion will tend to build Titanic Hydra second as it does a lot of damage based on your max health. Bruiser Sion is generally slightly less tanky than full tank Sion but can do much more damage. This build works because there are many bruiser/tank items that work based on your max health and Sion naturally has a large health pool because of his W - Soul Furnace passive. Generally, Sion mains like to build bruiser most games in solo queue as it allows for more carry potential. If you feel like you have no impact on Sion after winning your lane often, maybe try out bruiser Sion.

AP Sion

AP Sion is very fun to play but definitely less viable than his other builds. Try it out for a ton of fun in normals but I would not bring it into ranked unless you are able to consistently do well with it. Sion's AP scaling is not horrible but it's not quite up to par with other AP champions and he only has 2 abilities with ap scaling (his e and his w). If you want to change it up every once in a while with Sion I'd definitely try it as it's a very fun build. This build has some solid burst while still having the great utility and CC that Sion provides.

Smite lane Sion can no longer be a viable build as jungle items were removed with the item rework so there is no reason to take smite top.

• Sion's ult Unstoppable Onslaught can damage towers. You can use this to get a surprising amount of damage off (more if you are building AD). Keep in mind, you should not be ulting a tower unless you have minions near the enemy tower as allied minions lower the resistances of the tower by a significant amount. Your ult does more damage the further away you use it as well so consider walking back a bit before ulting a tower. The best use of this is when you are pushing for the end of the game. If you have minions on the enemy Nexus towers ult from just behind an enemy Inhibitor, aim for the middle in between the two towers. Instead of directly ramming into one tower cancel your ult in the center between the two towers. This will do damage to BOTH Nexus towers. This can easily do 700-800+ damage to both Nexus towers at the same time and much more if you are building AD.
  
• Sion's passive Glory in Death can be used to "cheese" the enemy jungle camps level one. If you are on blue side you can go to the enemy raptors at level 1, make sure the area is clear. If the area is clear attack the raptors and get very low health, when you are about to die start running towards the red buff. When you die use your passive to steal the red buff, you WILL keep the red buff when you respawn, TP back to lane after you steal the buff. If you are on red side you can do the same thing but with the enemy blue buff. There are two ways of doing it on red side. You can get low on wolves then run over to blue buff and kill it with your passive. The other way to steal on red side is to attack the blue buff then attack the gromp, stand in between both to keep aggro. When you die kill blue buff with your passive then kill gromp with your passive. TP back to lane after with your blue buff!
  
• Despite what many people think Sion is NOT a strong late game champion. Sion is strongest in the mid game. Use your mid game powerspike to make plays, you will be a lot stronger than most enemies at this point. The longer the game goes the harder it will get, their ADC and any Liandry's mage will shred you late game.
  
• Another misconception is that Sion is an engage champion. While this is partially true, Sion is not a reliable engage and serves best as a followup to another ally's engage. Sion's abilities are much more useful when an ally is able to CC the enemies first. Sion, for this reason pairs really well with engage tanks such as Sejuani.
  If a Sejuani ults for example, you can follow with your ult into Q and CC multiple enemies for several seconds, this should be enough to win a teamfight. With the help of another tank you can CC lock enemies for their entire lifetime.
  
• Take a moment every game to see what your team needs. Do you need to engage or peel? If you have a fed ADC and he is dying easily stick to him like glue. If your ADC gets really fed and you do not have a tank support on your team look to buy Knight's Vow and/or Locket of the Iron Solari.
  
• Sion can "jump" over player-made terrain such as Azir R Emperor's Divide, Anivia W Crystallize, Trundle's E Pillar of Ice, Yorick's W Dark Procession, and Jarvan's R Cataclysm. To pull this off you have to use your ult as Sion Unstoppable Onslaught and run at the terrain. Right before you hit the terrain cancel your ult and you will jump over it. The interaction with Azir's wall is the buggiest and may only work sometimes. The best way to jump over Azir R is to hop over AS he casts his ult. Here's a great video by Vandiril showcasing this trick:
• Sion's R Unstoppable Onslaught makes him immune to CC while active but does not break any existing CC. This means abilities such as Nasus' Wither will make your ult start a lot slower.
  
• Use Sion R to block the CC of an incoming gank instead of flashing. An example would be if you are getting ganked by an Elise and if she lands her Cocoon you know you will die. Instead of flashing her Cocoon, ult for the CC immunity and run to safety. Don't do this if your ult could be block by terrain or enemy champions. It's more important to use your ult than flash here because your ult is a way shorter cooldown and is generally less valuable than flash.
  
• Enemies CANNOT see Sion's Q Decimating Smash cast if Sion is hidden in a bush while charging. You can use this to great effect toplane by full charging Q's from the bushes while the enemy is trying to CS. If you do this enough, the enemy will be scared to walk near any bush without vision.
  
• Sion can buffer his E Roar of the Slayer into flash. Press E then flash instead of flash then E. This is much faster than flashing then E'ing and can make the difference in getting a kill or not.
  
• A simple way to surprise kill an enemy is to charge up your W Soul Furnace shield then E Roar of the Slayer + Flash and at the same time pop your W Soul Furnace and flick Q Decimating Smash for a surprising amount of burst damage. I have done this countless times to catch my opponent off guard. No one expects you to burst them like that. The best way to do this is when the enemy is low under tower and is overstaying for CS and XP. They will have very little time to react with this combo.
  
• Sion's E Roar of the Slayer no longer does increased damage when throwing a minion at an enemy. It now will apply the armor reduction though as an AOE, all enemies hit by the minion you throw will have their armor reduced. Try to throw a minion and hit multiple enemies during or before a teamfight to reduce their armor. If you manage to hit a few and your allies are nearby look to ult.
  
• Sion's ult Unstoppable Onslaught is very easy to land if you land your E Roar of the Slayer first. Like stated before, if you can throw a minion from far away and hit someone you can look to ult. This is one of the best times for you to use your ult.
  
• Sion can ult through many areas that people may not know. An example of this is ulting from your base to Baron or Dragon. I would recommend going into the Practice Tool and practicing these ult paths. Many of these are very difficult to pull off and I would not recommend attempting them in a ranked game unless you are very comfortable. Here is another great video by Vandiril showing many of the paths you can take:
• Sion's R Unstoppable Onslaught can essentially bounce off of many walls. You can use this to get some very unique angles on your ult. This is usually pretty inconsistent and you have to hit the right spots in the walls. Sometimes your ult will just end by hitting a spot in the wall while other times you will bounce off it and make a cool play. The best way to be consistent with this is to start parallel to a wall and slowly approach the wall at a 10-15 degree angle. If done correctly you will bounce off the wall! Keep in mind this does not work on every wall, in general it works with walls that bend slightly. A great example of this is right next to the bot lane tower where the wall starts to bend.
  
• You can use the F-keys (f1,f2,f3,f4,f5) to move your camera WHILE in Sion's R Unstoppable Onslaught. You can use this to get a more reliable view of what is going on. This is great for when you are ulting down mid lane or bot lane for example so you can see where your ally is in relation to the enemy. The F-keys are organized by your scoreboard. F1 is always you, F2 is the next person on the scoreboard and so on. If I was ulting down mid and I was the top laner I could quickly press f3 to look at my mid laner if he is fighting. This is kinda tricky to get the hang of but it is pretty easy if ulting in a near straight line like down a lane.
  
• Wait for enemies to use their movement abilities before you ult, it will make it much easier to land.
  
  

Sion Changelog

Up to date as of (US) 3/3/20 (Patch 11.5, season 11)

Patch 10.21
Q - Decimating Smash
DAMAGE RATIO TO MONSTERS 1.0 attack damage ⇒ 1.5 attack damage

Patch 10.19
Bugfix.
W - Soul Furnace PASSIVE BUGFIX When active, Sion's W - Soul Furnace now properly grants him bonus health from kills.

Patch 10.5
Bugfix.
If Sion channels R - Unstoppable Onslaught for 3+ seconds and then runs into an enemy champion, he now properly stuns the target for the intended 1.75 seconds

Patch 9.23
Bugfix.
When Sion casts R - Unstoppable Onslaught out of its range, the ability will now properly cast immediately instead of after he walks into cast range

Patch 9.19
W base shield increased.
W - Soul Furnace
BASE SHIELD 30/55/80/105/130 ⇒ 50/75/100/125/150

Patch 9.16
Base Stats
MANA 325.6 ⇒ 330
HEALTH 542.64 ⇒ 545
MANA REGEN 8.0008 ⇒ 8

Q - Decimating Smash
BASE MINIMUM DAMAGE 20/40/60/80/100 ⇒ 30/50/70/90/110
BASE MAXIMUM DAMAGE 60/120/180/240/300 ⇒ 70/135/200/265/330
REMOVED REDUCED DAMAGE ON MONSTERS Decimating Smash no longer deals 80% damage against monsters

Patch 9.3
Q damage decreased. W cooldown increased early.
Weakening Sion's early lane to make bad matchups more punshing for him.

Q - Decimating Smash
MINIMUM DAMAGE : [30/50/70/90/110]
⇒ 20/40/60/80/100
FULL-CHARGE DAMAGE : [90/150/210/270/330]
⇒ 60/120/180/240/300
W - Soul Furnace
COOLDOWN : [11] ⇒ 15/14/13/12/11 seconds

v8.20
Base health regen decreased.
Less health regen means Sion will have to rely more on his shield and health bonuses from last-hitting to stay healthy in lane.

Base Stats
BASE HEALTH REGEN : [9] ⇒ 7.5 per 5 seconds

v8.16
W health gain increased.
W - Soul Furnace
MAXIMUM HEALTH GAIN FROM ENEMIES : [3] ⇒ 4
MAXIMUM HEALTH GAIN FROM LARGE ENEMIES : [10] ⇒ 15

v8.14
Q base damage and damage ratio increased at later ranks.
Sion's last round of nerfs was necessary while Banner of Command was the top pick for top laners. Now that the item has been removed from the game, he's landing on the weak side.

Q - Decimating Smash
BASE DAMAGE : [30/47.5/65/82.5/100]
⇒ 30/50/70/90/110
DAMAGE RATIO : [0.45/0.50/0.55/0.6/0.65]
⇒ 0.45/0.525/0.6/0.675/0.75 total attack damage

v8.10
Base health regen decreased. E base damage decreased, damage ratio increased, and no longer deals bonus damage to secondary targets. E Armor shred now applies to secondary targets; duration increased.
The bonus damage Sion does to secondary targets struck by Roar of the Slayer is just too much: too much waveclear, too much poke, too much long-ranged lane control. By having E apply the armor shred to all targets struck, Q damage will be higher on targets struck by E, and further incentivize him to max Q (or at least to ensure there are more tradeoffs when he does opt into the ranged control E offers).

Base stats
BASE HEALTH REGEN : [10] ⇒ 9 per 5 seconds
E - Roar of the Slayer
BASE DAMAGE : [70/105/140/175/210]
⇒ 65/100/135/170/205
ABILITY POWER RATIO : [0.40] ⇒ 0.55 ability power
SECONDARY TARGET DAMAGE : [130%] ⇒ 100% to targets struck by a knocked-back enemy
ARMOR REDUCTION : [20% to primary target] ⇒ 20% to all targets hit by Roar of the Slayer or a knocked-back enemy
ARMOR REDUCTION DURATION : [2.5] ⇒ 4 seconds
R - Unstoppable Onslaught
COMING THROUGH Sion's ultimate is no longer obstructed by an allied Azir's Emperor's Divide

v8.8
Q damage ratio decreased at earlier ranks.
Sion doesn't currently sacrifice much damage in order to max Roar of the Slayer instead of Decimating Smash. In return he gains strong ranged poke, which is making him a dominant pick not only in top lane, but also mid in some matchups. There are times when it should make sense to max E first (ranged harass, using the slow to make Q easier to hit), but we want to make this less of a clear-cut choice.

Q - Decimating Smash
DAMAGE RATIO : [0.65] ⇒ 0.45/0.5/0.55/0.6/0.65 total attack damage
FULL CHARGE DAMAGE : [1.95] ⇒ 1.35/1.5/1.65/1.8/1.95 total attack damage

v8.5
Bugfixin'.
Roar of the Slayer

BOWLING WITH SION : Fixed a bug that made Roar of the Slayer's pass-through damage radius much wider than intended
BOWLING WITH SION IN THE JUNGLE : Jungle monsters launched by Roar of the Slayer now properly damage enemy champions

v7.22
BASE ARMOR : [23.04] ⇒ 32
BASE ATTACK DAMAGE : [59.72] ⇒ 68

v7.16
W grants more health for killing small units. R’s max damage increased.
Sion never truly recovered from midseason’s durability item changes. Through this lens, giving him the means to win back some late-game tankiness is fairly straightforward. Past that, we’re packing more punch into Unstoppable Onslaught to bring Sion’s teamfight initiation up to a more appropriately threatening level.

W - Soul Furnace
BONUS HEALTH PER SMALL UNIT KILLED : [2] ⇒ 3
BONUS HEALTH PER LARGE UNIT KILLED : 10 (unchanged)
R - Unstoppable Onslaught
MINIMUM DAMAGE : 150/300/450 (unchanged)
MAXIMUM DAMAGE : [300/600/900]
⇒ 400/800/1200
BUGFIX : Sion is now properly immune to Lulu's Polymorph during Unstoppable Onslaught

v7.11
W cooldown decreased, shield’s max health scaling increased.
Sunfire Cape followup buffs!

W - Soul Furnace
COOLDOWN : [13] ⇒ 11 seconds
SHIELD SCALING : [6/7/8/9/10%] ⇒ 8/9/10/11/12% Sion’s maximum health

v5.23
Sion
ATTACK RANGE : [150] ⇒ 175

v5.22
tell them how you really feel, sion
E - Roar of the Slayer
I'M NOT YELLING : Fixed a bug where yelling at an airborne minion would deal no damage
In a world without mana potions (and generally less early mana regeneration), we've identified a few champions for some emergency rations, giving early mana boosts until they can get their footing and purchase items to make up the deficit. This also means we can really understand which champions relied on mana potions as a crutch to limp through the early to mid game, and we can give additional love if necessary.

Mana

The following champs have +50 base mana and -3 mana scaling (net -1 mana at level 18):

v5.10
"Weird bugs, man."
R - Unstoppable Onslaught
USE YOUR OWN AXE, SION : Fixed a bug where Unstoppable Onslaught was scaling with the target's bonus attack damage instead of Sion's

v5.8
W's health ratio is lower at early levels and takes longer to reactivate.

"The undead hulk that is Sion dies more often to jungle monsters than champions these days, mostly due to the strength of Soul Furnace. While we like that he takes a lickin' and keeps on tickin' (do zombies tick?), Soul Furnace's offensive capability often seals a winning lane for him once he's able to build enough Health, creating a situation for opponents where beefing up makes the shield's damage more effective (as it scales off an enemy's maximum health), while building more damage to pop Soul Furnace opens them up to being crushed by a Decimating Smash. Limiting his shield's flexibility offensively while keeping it sturdy enough to mosh 5v5 should keep him as threatening as ever without being a catch-all solid pick. "

W - Soul Furnace
SHIELD DETONATION TIMER : 2 seconds ⇒ 3 seconds
RATIO : 10% maximum health ⇒ 6/7/8/9/10% maximum health

v5.6
Q hurts monsters less. E's passthrough damage down.

"Primarily thought of as top tier laner, Cinderhulk saw Sion shamble on into the jungle and dominate without breaking a sweat. The changes themselves are simple enough, but underscore an important point - Sion should be a powerful pick for the crowd control and durability he brings to a composition, not necessarily his damage output (especially when building tank)."
Decimating Smash.png Q - Decimating Smash
DAMAGE TO MONSTERS : 90% ⇒ 80%
Roar of the Slayer.png E - Roar of the Slayer
PASSTHROUGH DAMAGE BONUS : 50% ⇒ 30%

v5.5
Q's mana costs down, ratio slightly up. E's mana costs up at later ranks.

"When it comes to Super-Tanks in top lane, we actually like what Sion brings to teams and how he interacts with opponents, with the exception of his laning phase - so we're keeping things "power-netural" for the big zombie. Shifting power from screaming at minions to dropping the chopper on frightened opponents means it requires a little more effort to win the wet-noodle-war than just never running out of mana. "
Q - Decimating Smash
COST : 45/50/55/60/65 mana ⇒ 45 mana at all ranks
RATIO : 0.6-1.8 total attack damage ⇒ 0.65-1.95 total attack damage
E - Roar of the Slayer
COST : 35 mana at all ranks ⇒ 35/40/45/50/55 mana

v5.1

"Zombies already have Grievous Wounds, man."
Passive - Glory in Death
FOR THEMATIC REASONS? : Fixed a bug where if Sion was killed while affected by a healing debuff (ex. Grievous Wounds), he would revive in his zombie form with reduced health
"We're making readability improvements to a bunch of the champion portrait icons which were added or updated over the past few months."
PORTRAITS : The following champion portrait icons have been updated:
Azir, Cho'Gath, Ezreal, Gragas, Graves, Janna, Jarvan IV, Kayle, Kog'Maw, Lee Sin, Malphite, Maokai, Orianna, Renekton, Rengar, Rumble, Shyvana, Sion, Talon, Tristana, Udyr, Vayne, Veigar, Viktor, Zilean

v4.20

Glory in Death's health drain has been lowered for higher levels and Sion's health regeneration growth stat has been lowered a bit.

"Sion's been climbing the ranks towards Mundo-hood when it comes to overall longevity and, couple that with the 2015 changes to regeneration, we have a real monster on our hands. In light of that, we're mainly re-mathing out Sion's passive to favor the juggernaut's beefier builds. "
General
HEALTH REGENERATION GROWTH STAT : +1 health per 5 seconds ⇒ +0.8 health per 5 seconds
Passive - Glory in Death
HEALTH DECAY : 2 x level ⇒ 1 + (1 x level)
HEALTH DECAY GROWTH : 1.4 x level ⇒ 0.7 + (0.7 x level)

v4.19
Lots of bug fixes along with a small mana cost shift from Sion's Q + W to E.

"We've got a little room to give Sion some post-update love, so we decided to focus on his best stat: health. Additionally, we've made a lot of quality-of-life changes & bug fixes to help Sion be the best he can be. Final note for that passive change, we changed it because it was punishing Sion for building HP, which was dumb. Now health-stacking Sion should stay up a little longer in his zombie form in comparison to a damage-focused, low-health Sion. Logic! "
General
HEALTH PER LEVEL : +70 ⇒ +73
Passive - Glory in Death
COMPLICATED ZOMBIE MATH : Sion's health decay in passive form now scales with his max health (0.5% max health first tick, increasing by 0.4% max health per tick) ⇒ champion level (2 x level first tick, increasing by 1.4 x level per tick)
FIERY DEATH : Fixed a bug where Sunfire Cape wasn't working while Sion was in his passive zombie state
YORICK IS HELPING : Glory in Death no longer fails to activate in cases where Sion is targeted by Yorick's Omen of Death, doesn't trigger the revive effect and then dies later on in the match
Q - Decimating Smash
COST : 50/55/60/65/70 mana ⇒ 45/50/55/60/65 mana
SMASHING PARITY : All crowd-control types now correctly refund Decimating Smash's cooldown to 2 seconds when they interrupt Sion while he's charging up
YELLING AND SMASHING : Sion can now properly cast Decimating Smash immediately after Roar of the Slayer
W - Soul Furnace
COST : 70/75/80/85/90 mana ⇒ 65/70/75/80/85 mana
PASSIVE HEALTH GAIN : 8 ⇒ 10 on large monster kill and champ kill/assist (minion and small monster bonus unchanged)
E - Roar of the Slayer
IT'S A JUNGLE SION BUFF : ⇒ Knocked back minions are no longer invulnerable to damage while in flight but can't be killed before landing unless Sion casts Smite on them
COST : 25 mana at all ranks ⇒ 35 mana at all ranks

Source: https://lol.gamepedia.com/Sion