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Sion Build Guide by WavFM

Top "Slay the strong, trample the weak!"--Sion Guide

Top "Slay the strong, trample the weak!"--Sion Guide

Updated on February 25, 2023
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League of Legends Build Guide Author WavFM Build Guide By WavFM 1496 85 2,878,764 Views 91 Comments
1496 85 2,878,764 Views 91 Comments League of Legends Build Guide Author WavFM Sion Build Guide By WavFM Updated on February 25, 2023
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Choose Champion Build:

  • LoL Champion: Sion
    Tank Sion
  • LoL Champion: Sion
    Lethality Sion
  • LoL Champion: Sion
    Support Sion
  • LoL Champion: Sion
    Jungle Sion

Runes: Grasp (vs most matchups)

1 2 3 4
Grasp of the Undying

Biscuit Delivery
Approach Velocity

+10% Attack Speed
+9 Adaptive (5.4 AD or 9 AP)
+6 Armor


1 2 3
LoL Summoner Spell: Flash


LoL Summoner Spell: Teleport



Starting Items
Standard start
Against poke (Teemo, Jayce, etc)
Boot Options
Against AP/heavy CC
Anti-slow (vs. Nasus, Aatrox, etc.)
Early Item Options
Standard (Heartsteel rush)
Against healing
Waveclear (Sunfire rush)
Against heavy auto attacker
Mythic Item Options
Best in most games
Vs. ranged or getting kited
OK in some scenarios
Good Armor Options
Must buy in almost every game
Antihealing and dmg
Against crit
Mana and att speed slow
Good MR Options
Ability haste and shield size
Team damage and regen
Good Peel Options
Protect the carry
Cleanse CC for ally
Boost ally damage
Aoe heal and damage
Good Health or Mixed Resist Options
Health and regen
Vs. fed hypercarry/splitpusher
Armor + MR and shield
Good Damage Options
Auto attack damage
Damage and shield
Splitpush (nerfed, not recommended)

Threats & Synergies

Threats Synergies
Extreme Major Even Minor Tiny
Show All
None Low Ok Strong Ideal
Extreme Threats
Ideal Synergies
Ideal Strong Ok Low None

Champion Build Guide

"Slay the strong, trample the weak!"--Sion Guide

By WavFM
About Me
I have been a Sion main since his rework, he has been my most played and favorite champion since season 5. In Season 6 I reached diamond with a 68% winrate on him over 169 games. I recently changed my name from Stinkee to WavFM on the site, so if you see any past comments from Stinkee, that's me.


Why Sion?

Sion is, in my opinion, the most versatile tank in League of Legends. He is able to adapt to each game in a way that is unmatched by any other. He can be played as a full on tank, a tanky bruiser, a splitpusher; many even play Sion as an AD assassin or bruiser including Thebausffs and Tilterella both, at one point, 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. He also has a very low pick and ban rate, making him a great champion to main or one-trick. Sion is very easy to learn but also has a lot of potential for skill expression, solidifying him as both a great champion for new players and for masters alike.

How to use the guide

Tanks, moreso than other roles must build items based on the factors unique to each game. Because of this, you should use this guide as a foundation to find your own way to play that works for you. Don't strictly follow a full build, instead, learn each of the item options and how to adapt to each game. The full builds I showcase are just examples and will not be ideal in every situation or game.
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, which grants a burst of Movement Speed.
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.


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.
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.

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.
View the Sion Matchups section under the "Tank Sion" 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


In general, Sion is countered by high mobility, %hp damage, hard CC/skillshots, and bruisers. All of his abilities are very telegraphed, making them very easy to predict and dodge. 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.


Since Sion has very telegraphed but hard hitting abilities, he pairs very well with other champions that have easier to land/setup CC. His 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.

Grasp of the Undying is really the only viable keystone in this tree for top and mid lane. 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 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.
Any option is viable in this tier but Overgrowth is usually the best rune option. 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.
Magical Footwear is a fairly viable option for the secondary tree. Even so, I only recommend taking it over something like Biscuit Delivery into very easy matchups.

Biscuit Delivery is a pretty great rune choice for Sion. Sion tends to run out of mana fast and has no form of health sustain so the extra sustain that the bicuits provide is really nice. They also increase your maximum mana. I would consider taking Magical Footwear instead (if inspiration is your secondary tree) if you believe you will have an easy lane. 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 keep up with the enemies.


For Sion's first purchase you can decide to go Corrupting Potion or Doran's Shield + Health Potion.

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.


Sion can go Plated Steelcaps, Boots of Swiftness, 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. Boots of Swiftness is an option that can be taken in any game and is a solid option if you want more mobility instead of resistances.


Heartsteel: Heartsteel is the perfect mythic item for Sion and it should be your default purchase in most scenarios. It does a ton of damage and scales really well. It also gives Sion another way to infinitely stack health. The only big downside of this item is that it doesn't give resists and sometimes resists are just better. You could have 10,000 bonus health but it doesn't matter if someone has tons of percent health damage in their kit or in their items. That said, you can still get your resists from other items; just keep in mind that this item may not make you as tanky as you think in many cases.

Iceborn Gauntlet: Frostfire Gauntlet is an improved Iceborn Gauntlet from the previous seasons. 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. It also provides a decent chunk of armor which is borderline necessary in some matchups. 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.

Jak'Sho, The Protean: Jak'Sho, the Protean is a pretty well-rounded item. It gives both armor and magic resist as well as health. Its passive is great for teamfights. This item can be great if you just need lots of resists in a specific game and/or you are teamfighting a lot. You could also buy this as your default mythic instead of Heartsteel if it's your preference but I personally find Heartsteel to be stronger in most scenarios.


Sunfire Aegis: Sunfire is the perfect offensive tank item and now that it is a legendary item, you can easily buy it every game. You can even buy it first item if you need the armor and wave clear. The damage of Sunfire scales with your bonus health and as Sion you have a TON of bonus health, especially if you are buying Heartsteel as well. The only situation that I'd consider NOT buying Sunfire is if the enemy team is very heavily weighted towards magic damage and/or you just need to focus on defenses and peeling.

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. It makes a big difference, especially if you are the only one on your team with healing reduction. Rush Bramble Vest against champions like Nasus and Fiora, who look to heal/lifesteal a lot in lane. This REALLY helps you win trades and the lane as a whole.

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.

Winter's Approach: This is an item that I have wanted them to make for a long time. A tear stacking tank item. This is a great option for Sion. Sion naturally has low mana and low mana regeneration while having high mana cost abilities like Soul Furnace. This means spamming your abilities will cause you to run out of mana VERY fast. This item is a nice a remedy to that issue. If you are like me and like to constantly pressure your opponent by spamming abilities, I highly recommend this item as a first or second purchase.

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. This item also pairs really well with Spirit Visage or even Mikael's Blessing increasing your shield size by an additional 25% or 20% respectively.

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.

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.

Anathema's Chains: Anathema's Chains is a situational item. This item works really well if there is one very fed enemy on the opposing side. However, it is not that great of an item in any other scenario. Don't buy this item every game. Do consider buying it if there's one fed hypercarry that will 1v9 the game on the enemy team. Think of a 15/1/0 Master Yi at 15 minutes, yeah you definitely should buy this item in that situation. But, imagine the enemy team has 15 kills and 1 death total but it's spread evenly between their entire team. All 5 enemies with 3 kills each. Anathema's Chains isn't going to be useful at all in that situation.

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.

Hullbreaker: Hullbreaker was recently nerfed. I don't recommend buying this item anymore. There are just better items out there for Sion. If you want to do some damage and occasionally split push, I would just go a Titanic Hydra tank build instead.

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.

Mikael's Blessing: I'm currently testing Mikael's as an alternate (or additional) magic resist item. The mana regen could be very useful on Sion as he tends to have mana issues. Mikael's is also WAY cheaper than other MR items while still providing a significant, 50MR. It also has 15 ability haste, 100% base mana regen, and 20% heal and shield power (which would be great for Sion's W Soul Furnace). It is only 2300 gold and the only thing it is really lacking that the other magic resist options provides is health. Mikael's gives 0 health. But, it is so much cheaper and the unique active of being able to cleanse CC could be great if you have a fed hypercarry on your team that needs peel. This item also makes buying an early Faerie Charm viable for mana regen as you can upgrade it into Mikael's later. Overall, I definitely need to test it but it could potentially be a viable option for Sion (and other tanks), and another (maybe niche) alternative to the other MR items. Thanks to Heansuh in the comment section of this guide for the idea!
Why tank?
Building tank on Sion is the standard way to play him. His kit is designed to be played that way. His build can be very versatile and he can be played in any lane or jungle to an extent. He also has the option to buy 1 or 2 more damage focused items like Titanic Hydra or Sterak's Gage due to the insane AD ratio on his Q Decimating Smash. Your goal as a tank will differ from game to game. If your team needs an initiator, you can fill that role, otherwise you can try to peel your teammates.

Top Lane
Top lane is the most popular and usually the best lane to play tank Sion in. Tanks in general top lane should focus on surviving lane until they get enough gold to buy tank stats. The first few levels can be rough as you're not really a tank yet. Once you buy your first tank item or two, you should be able to brawl with most top laners and win. Tanks become really strong in the mid game when they get their first few couple of items. In the mid game you should look to help your teammates. You can either initiate for picks or teamfights or peel for your fed carry. Once the late game approaches, you may notice you will feel a bit weaker. Tanks aren't great late game because enemy carries (usually the ADC) have reached their power spikes. These carries take longer to come online which is why you are stronger than them until this point. Still, you can make a massive impact as a tank late game, you will just need to be more cautious and focus more on peeling than engaging, depending on the gamestate.

Mid Lane
Mid lane Sion is played basically the same as top Sion. One thing you can do mid that you can not do as top as much is roam with your ult. A great play you can make mid is to slow push 2-3 waves of minions then roam bot or top with your ult. Matchups mid are actually pretty great. Most mid laners are burst heavy but since you are a tank, you can absorb all of their damage and turn on them once their abilities are on cooldown. Against ranged matchups mid, look to E a minion at them then run up and W + Q and auto them for a great trade. You can afford to take Unsealed Spellbook or Glacial Augment against most matchups mid. This is because against ranged mid laners, you will not be able to proc your Grasp of the Undying very often. Against melee mids you can still take Grasp of course.
Why lethality?
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.

Some tips
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. Several Sion mains have managed to reach Challenger one tricking AD Sion, it's definitely viable but keep in mind, it is difficult to learn and master.
Why support?
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.

Some tips
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.

Keep in mind, the reason support Sion isn't picked very often is because of his W - Soul Furnace. As support you will barely get any stacks meaning you will be much, much easier to kill than mid/top/jungle Sion. It can still be a good pick, though it may require some more skill and effort than his other positions.
Why Jungle?
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.

Some tips
Sion's weaknesses in the jungle remain, he does 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.

For ganks you should make use of lane bushes and go for lane ganks. You can sneak into a bot or top lane bush (if it's not warded) and wait for the enemy to walk up and full charge your Q - Decimating Smash. After level 6 you can ult down the lane or through the river and jungle.

Jungle Sion can be played as tank or full AD. For the clear I recommend checking out Timothy Fly on youtube. He's a master tier Sion jungle main with several guide videos on jungle Sion. He focuses mostly on AD Sion but you could apply most of his tips for tank Sion.
Tips and Tricks
Glory in Death (Passive) Tips
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 killing blue buff.

Please note that killing the blue buff while in Sion passive is actually bugged right now and you WILL NOT keep the blue buff when you respawn, hopefully they will fix this issue soon.



Glory in Death is incredibly useful at level 1. It can actually be worth it to intentionally die in an invade to gain access to this overpowered level 1 ability. You can usually trade your life for 2 kills at level 1 with this. Just make sure you're in a good spot when you die or they will just run or Flash away.

All active items can be used while in Glory in Death. This is why a lot of lethality Sion mains will rush Prowler's Claw, to close the gap.

Decimating Smash (Q) Tips
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.

Sometimes going for the stun with Decimating Smash is not worth it or not possible. Flicking the Q (just tapping it or holding it for <1 second) is still a good source of damage and a decent slow.

If your Q doesn't look like it's going to hit, it's not always best to immediately cancel it. Decimating Smash is still a great zoning tool, preventing enemies from entering the area. This should really only be done if you have an ally with you who can take advantage of your zoning.

If you are hard CC'd while charging Q, it will only go on a 2-second cooldown. Most of your enemies will not know this and will not expect you to be able to charge a Q again shortly after they cancel it. Sometimes it's actually worth it to let them cancel it if they'll need to use an ability with a long cooldown to do so.

Decimating Smash is one of the most powerful abilities at level 1 in the right circumstances. It may be the single best ability in the entire game to counter a 5-man invade. If you expect an invade, tell your team to camp a bush with you. When the enemy team walks up, start full charging your Q. You can usually hit 3+ with the full charged Q at level 1, effectively Amumu ulting them at level 1 and ensuring that your team will win the skirmish.

Soul Furnace (W) Tips
For maximum efficiency of this ability when fighting always try to use the second part (the explosion) just before the shield is about to be destroyed by the enemy. This is a small thing but it really adds up when trading top lane.

If you need to quickly burst someone to execute them you can charge up Soul Furnace, when it's ready to pop, [flash] and press Unstoppable Onslaught and Soul Furnace again, then flick Decimating Smash. This combo does a lot of damage and catches enemies off guard. This is especially useful when the enemy is overstaying under tower. You may not even need to use Unstoppable Onslaught depending on how low they are.

Roar of the Slayer (E) Tips
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.

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.
Unstoppable Onslaught (R) Tips
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 Ult Damages Towers

Sion can "jump" over player-made terrain such as Azir R Emperor's Divide, Anivia W Crystallize, Trundle E Pillar of Ice, Yorick W Dark Procession, and Jarvan IV 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 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 blocked 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.

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. Also, if you land your E and you took the Approach Velocity rune, you will gain movespeed, making it easier to land 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.

Sion Ult F-Keys

General Tips
Before each game, look up your lane opponent's movement ability cooldowns. For example, if I'm Sion and I see Riven on the enemy team, I will look up the cooldown of her E and her Q (her dash abilities). This will allow me to have an estimate how long I have until she has dashes again. Doing this will help you land your crucial abilities like Decimating Smash and Unstoppable Onslaught.

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 Anguish build mage will shred you late game.

Another misconception is that Sion is an engage champion. While this is partially true, Sion is not a very 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 other support items after your first couple items.

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.
League of Legends Build Guide Author WavFM
WavFM Sion Guide
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"Slay the strong, trample the weak!"--Sion Guide

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