Hi everyone. I'm TheMistCollector, TMC or Mist for short. as you can guess from my name, I'm a Senna OTP, since she was out on PBE. I started playing at the end of season 7 and I got to Plat last season, it's my highest rank ever, and my goal this season is to reach Diamond (UPDATE: I DID IT :D next goal: Masters UPDATE 2: YOOO I'M MASTERS BABY UPDATE 3: GRANDMASTER, I'M GM UPDATE 3 I GOT TO CHALLENGER!!!). I know, it's not such a good elo (IT IS NOW), but the fact that she's the first and only champion that i mastered, and i have a lot of free time, I consider myself experienced enough with the champion to bring you a complete guide on her with no flaws.



Before Senna, I was a Support main, but i've always enjoyed Marksmen playstyle. When Senna got revealed, i knew she was my champion. I was there day 1 analyzing and theorycrafting with Senna, along with others... So yeah, i feel like i really know about this champion.

Btw this is my first time making a guide, so sorry for any inconsistencies and for no fancy table of content and all of that.

THIS GUIDE WILL GET CONSTANTLY UPDATED, any big change that affects Senna will be addressed. Additionally, i'm constantly theorycrafting new items and builds, if i find something OP, i will share it.

Also, english is not my main language, so if you don't understand a section of the guide or you find a small typo, please let me know!

(Apologies for the format getting kinda messy towards the end of the guide for mobile users).

First of all... What does Farming and Fasting even means?!

Farming/ADC

This is your conventional ADC strat. You start normal ADC item, with a normal Support, you farm minions, take kills... Just as a normal ADC, nothing weird here. Throughout this guide i will be using both "FARMING" and "ADC", just so you know that i'm talking about the same thing.

Fasting

This is an alternative strat that revolves around Mists. You go Support item first, and your duo (non-marksmen) farms with normal starting item. This strategy allows Senna to "protect" her duo by poking so they can farm safely, while she gets fed with Mists and kills. Suddenly in late game, you have a champion with crazy DPS and tons of utility (almost covering both ADC and support role), and another champion with good damage and utility. Senna can take 1-2 melee minions per wave to reach her maximum potential. Minion gold, Support item gold, and Mists crazy gold efficency make this strategy so good.

PROS

• Mechanically simple champion
• Easy to learn
• Infinite scaling
• Playstyle versatility
• Skill expresion
• Uniqueness in both gameplay and builds
• Annoying to play against
• Cool concept/desing

CONS

• Bad early game when farming
• Bad mid game when fasting
• Very reliant on mists (No AD per level)
• Low elo tilting when fasting
• ADCs don't like to play with a Senna support (for some reason)
• Terrible when counterpicked
• Awkward AAs with low practice
• DuoQ reliant when fasting (unless Master+)

In this chapter i will talk about the standar runes for Senna, as well as some other popular (but not necessarily good) ones.

Main builds:

Fasting/Farming/Support Precision

Fleet Footwork: Welcome to Cut Down meta! Fleet Footwork is the only keystone here that Senna can blindly use. It gives a MS burst which is nice for an immobile marksmen, and the heal helps her play a bit more aggresively. The main reason we go for this though is because of the access to Cut Down. In 12.12b, Senna became the champion with the lowest base HP of the game with 530 ( Yuumi has 550... 13.1b UPDATE: Good news, Senna is no longer the champion with the lowest base HP in the game, bad news, it's not because she got buffed, but because Yuumi got nerfed. Basically, her HP is still low even if it's not the lowest one anymore). Because of this, Senna is the best champion to use Cut Down, and we should always use it when building for damage.

Lethal Tempo: After the 13.4 AS ratio buffs (from 0.3 to 0.4), this rune is now viable on Senna. I'd now say she uses every on-hit effect pretty effectively including this one. She stacks it consistently and the AS she gets is pretty good. Because she already has 600 base range, once it's stacked she can easily keep hitting champions in laning phase to keep the stacks and have 30-42% AS "permanently" alongside the extra range for your Q. After laning phase, this rune also has a really good scaling so you get a lot of extra DPS. I don't think this rune is that good to completely ignore Fleet, but it's good enough to risk your laning phase to use the rune for lategame DPS. Since ADC Senna doesn't want Fleet as religiously as Support/Fasting, this will be the best Standard keystone for her.

Press the Attack: This is an alternative rune in scenarios where Fleet Footwork is not needed and you will constatly fight early 2v2s. Senna can proc this rune pretty fast with Piercing Darkness and from a safe distance to not only boost her own damage, but her allies' too.

Support Resolve

Grasp of the Undying: Default rune for the Tank build, it helps with lane pressure with its healing and bonus damage (both scaling with max HP), but the main reason we go for this rune is the infinitely stacking Health. It's just an amazing synergy with the Tank build which is mostly Health stacking.

Guardian: Alternative, and weaker, keystone for the tank build. We lose a lost of synergy but there's going to be matches where you just cannot stack Grasp, so this is better than nothing. At least it also scales with Health, although not that much.

Fasting/Farming/Support Inspiration

First Strike: This rune is good on its own when building lethality, offering a small ammount of damage in the early game, growing as the match goes on. But the main reason we use this rune is for a number of facts combined, but can easily be explained with 1 word: Gold. First strike converts a portion of the damage dealt with it into gold, it allows us to use the Inspiration tree to access Magical Footwear and Future's Market, and because we're building Youmuu's Ghostblade, we can delay boots up to 3 items later to get our powerspike faster than everybody else in the match (this also means getting a faster use of First Strike). All of this combined with Spectral Sickle's fast gold generation, Senna's Absolution further inflating our gold (with 8 gold per mist we pick up from the ground), and our fast early spike with a Serrated Dirk to start getting early takedowns means that you will either be toe-to-toe with the enemy bot if you're in a naturally bad matchup, ahead in a naturally even matchup, and take over the game in a free matchup.

Popular rune choices:

Ultimate hunter: It's not worth taking it because Senna is not really reliant on Dawning Shadow. It's true that Senna's Ultimate has a lot of cooldown, but losing Precision tree for a couple more ultimates is not worth.

Triumph: Ignoring that this rune scales with Max HP (and Senna has the second lowest), it is also meant to be very Skirmish/Bruiser heavy since it allows you to sustain better throughout the whole fight. If Senna wants a defensive rune, Overheal Will be better, since it she's most likely either at full health, or dead/out of combat; you cannot afford to have survivality dependent on getting takedowns.

Cheap Shot: While it looks good on paper, when compared to Taste of Blood you realize that the latter is better (Not by a lot, but still better). They both look to gain early advantages, one via damage and the other via healing, but ToB scales infinitely better and it is easier to proc.

Coup de Grace: Cut Down DEALS MORE DAMAGE IN 105% OF THE MATCHES AND I'M NOT ONLY TALKING ABOUT SENNA (BUT SHE'S ONE OF THE BEST USERS BECAUSE OF HER EXTREMELY LOW BASE HEALTH), BUT EVERY MARKSMAN. STOP PICKING THIS GARBAGE RUNE!

Demolish: You outrange its proc range starting at level 1, so it's awkward to use from the start. Besides, the value of Font of Life in a health stacking build is too good to pass up.

In this chapter i will talk about the standar summoner's spells for Senna, as well as some other popular (but not necessarily good) ones.

Main spells:

Flash: This is the best summoner spell in the game, by far. It can be used both aggressively and defensively, and can be used with other abilities (mostly Last Embrace and Dawning Shadow) to create unpredictable situations for the enemy team. Not taking this summoner spell is trolling.

Barrier: This is the standar summoner spell for support, because double Heal is a bad option. it helps for general survivability. If your ADC doesn't go Heal, consider picking it if you don't need Exhaust.

Heal: This is the standar summoner spell for farming and fasting. It helps for 2v2 early fights and for late game survivability. Go for this if you don't need Exhaust or Cleanse

Exhaust: This is a good alternative. It is meant to counter assassins and skirmishers. Against these champions it's always more valuable than Heal, since it shuts down burst damage.

Ghost: Great alternative in matches where Movement Speed will make a great difference. It can be used both defensively (to disengage from a fight, to avoid a gank, etc) and aggressively (to chase down a target, to have better kite, etc).

Cleanse: This is a great summoner spell meant to counter heavy CC ( Ashe, Leona, etc.) or any undodgeable CC ( Twisted Fate, Annie, etc.). I always prioritize this over Exhaust since being CCd means that anyone can burst me down anyways. (avoid using this when playing support, unless you when don't need neither Heal nor Exhaust)

Popular spell:

Ignite: This is NOT a good summoner on Senna, doesn't matter the role. If you are at Ignite range, you are poorly positionated.

In this chapter I will show every ability of Senna, as well as giving general information and tips.

Passive - Absolution

Ability full description BASIC ATTACK: Senna blasts her target with her relic cannon, dealing 100% AD physical damage and applying on-hit effects. This attack does not use a projectile. Senna's basic attacks can critically strike, but they only deal (150.5% + 30.1% 30.1%) AD physical damage. Senna's attack speed benefits from only 20% of her total bonus attack speed (instead of 62.5%) and the attack's windup time is only reduced by 60% of the expected value given attack speed bonuses. Senna's attack windup is reduced by 100-(0.5 to 0.35)/0.5*100% (based on level). INNATE - WEAKENED SOUL: Senna's basic attacks on-hit and damaging abilities on enemy champions apply a stack of Mist for 4 seconds, modified to 0.75 seconds if Senna starts winding up a basic attack on them. Subsequent hits will collect Mist, dealing 1% − 10% (based on level) of target's current health as bonus physical damage, and rendering the target immune to further Mist applications for a few seconds. This damage applies life steal at 100% effectiveness. Enemies that die near Senna may spawn a Mist Wraith from their corpse. A Mist Wraith lasts 8 seconds and Senna can basic attack or hit it with Piercing Darkness Piercing Darkness or Dawning Shadow Dawning Shadow to kill them instantly, granting her 8 Gold 8 and collecting their Mist. Enemy champions and large monsters will spawn a Mist Wraith. Epic monsters will spawn 2 Mist Wraiths. Minions and lesser monsters that Senna kills have a 8.3% chance to spawn a Mist Wraith. Large minions that Senna does not kill will spawn a Mist Wraith, while lesser minions and lesser monsters that Senna does not kill have a 28% chance to spawn. MIST: For each stack of Mist, Senna gains 0.75 bonus attack damage. For every 20 stacks, she also gains 20 bonus attack range and 10% critical strike chance, capped at 100% critical strike chance. Additionally, 35% of the generated excess critical strike chance is converted into life steal. INNATE - RELIC CANNON: Senna's basic attacks on-hit deal 20% AD bonus physical damage and grant her 10 / 15 / 20% (based on level) of the target's movement speed as bonus movement speed for 0.5 seconds. This damage applies life steal at 100% effectiveness.

In a nutshell, Senna's auto attacks have reduced attack speed, deal reduced crit damage, doesn't use a proyectile, gives her movement speed and deal additional on-hit damage. Hitting an enemy champion with an auto attack or damaging ability 2 times grants Senna a Mist stack. Each Mist stack gives 0.75 AD, and gives 20 range an 10% Crit chance per 20 Mists (excess crit chance grants Lifesteal instead, up to 35%). Mists can also appear when a unit dies near Senna (chance is different for each unit, also affects if Senna is the killer.)

General tips:

• This is the most important ability in Senna's kit, since you don't have AD per level, it's important to have a high Mist per Minute ratio. 4 Mists per Minute (40 mists at 10 minutes. 100 mists at 25 minutes) when Fasting, and 2.5 Mists per Minute (40 mists at 16 minutes. 100 mists at 40 minutes) when Farming are good indicators that you're doing good.
  
• 40 Mists is a generous powerspike since you gain a lot of gold worth from stats (~1500 gold) and the 40 additional range makes you a much scarier threat.
  
• You can lifesteal out of Mist wraiths
  
• Ally champions who kill minions with Relic Shield or Steel Shoulderguards are considered killed by Senna for Mist Spawn Chance purposes.

Q - Piercing Darkness

Ability full description ACTIVE: Senna fires a spectral laser in the direction of the target unit, healing herself and allied champions in a line, and dealing physical damage to enemies in a thinner line. Upon being struck, enemy turrets, wards, jungle plants, Mist Wraiths and any other attack-interactive units are considered basic attacked once, while champions and turrets are applied on-hit effects at 100% effectiveness. Basic attacks reduce Piercing Darkness' cooldown by 1 second on-hit.

When to use:

This is your main ability, you use it to trade, for high DPS and huge healings in teamfights. If you have enough range you can pretty much hit all 10 champions with every Q, so think about your positioning.

General tips:

• You should constantly AA anything (if minions, make sure you don't mess up the wave for your ADC) because it reduces Q cooldown, allowing you to trade more oftne
• This ability can reduce its own cooldown when used against: Enemy turrets, enemy champions, jungle plants and enemy wards, meaning if you Q into AA against any of this things you will reduce 2 seconds of cooldown in no time.
• This ability cannot reduce its own cooldown when used against: Ally turrets, ally champions, ally and enemy minions, ally wards, jungle monsters (dragons, buffs, small camps) and mist wraiths.
• If you hit your Q against both a target that reduces its own cooldown and one that doesn't, regardless of target, it will still reduce it.
• If your Q hit multiple enemy champions, it will reduce its own CD by 1 second for each enemy champion hit
• You can use Q to clear enemy wards faster
• Sheen and other on-hit effects procs based on enemy Spawn ID.
• This ability is currently BUGGED (12.19 last check): If you use it while channeling Dawning Shadow the Q will go towards the ultimate's angle, not the Q target.

W - Last embrace

Ability full description ACTIVE: Senna throws a globule of Black Mist in the target direction that deals physical damage to the first enemy hit and sticks onto them for 1 second. After the duration or when the target dies, the Black Mist spreads out of the target, rooting them and nearby enemies for a few seconds.

When to use:

This ability is just a generic CC, you can use it to escape, lock a target, follow up a target or opening a follow up to your allies. You can also use this ability when warding to check brushes without risk.

General tips:

• You can W + Flash, the ability will be casted to target location from after-flash position. There is a bug that, when timed correctly, will make your W projectile look like its going from pre-flash position, but its hitbox is actually from after-flash position, making it look like it goes through enemies and suddenly hits a random target.
• You can look to kill a low hp minion close to an enemy champion with W to surprise them with an instant root
• Malzahar's Void Shift will block W damage, but not the root (as long as he is the main target).

E - Curse of the black mist

Ability full description ACTIVE: Senna surrounds herself with an aura of mist and gains camouflage for a duration. If Senna breaks the camouflage, she regains it after 1.75 seconds of not performing actions that break stealth. Allied champions who enter the mist gain Wraith Form for a duration equal to the remaining duration. WRAITH FORM: Gain camouflage. Enemies will have obscured vision of Wraiths moving outside of the mist. Wraith Form can be regained if lost by breaking the camouflage after 1.75 seconds of not performing actions that break stealth. Wraith Form ends immediately upon Senna's death. Senna and allies camouflaged by Curse of the Black Mist also gain 20% bonus movement speed.

When to use:

This ability is the most tricky ability to correctly use.In the early game, you can use it to chase, you can use it when your duo is walking from base towards the lane to surprise the enemy, you can walk towards river and bring your jungler to an easy gank, you can use to scape ganks/all-ins ( Ashe can't kill you without Enchanted Crystal Arrow if you have E for example).

In late game you can use it to catch isolated enemies with a teammate, or it can be used as an overall pressure since the enemy team don't have any information. This ability is super flexible! how you use it will make a huge difference between a noob Senna and an experienced one.

General tips:

• This ability is a big part of why Senna is annoying to play against, you can hide your whole team before a teamfight so the enemy team can't engage on anyone.
• In the early game, you can trick the enemy botlane by walking to the sides while your duo walks towards them to engage. (HIGH COORDINATION REQUIRED)
• Control Wards reveal you. after leaving the ward's area, you will be revealed for an additional 1.75 seconds before camouflaging again
• If there is a Control Ward out of vision while in E, it will be revealed, so you can take it without risk.
• You can use this ability when warding to get that extra survivability and movement speed, since squishy champions struggle to ward without being in heavy danger.
• This ability is currently BUGGED (13.7 last check): Seemingly random abilities can target you even when you're camouflaged. Instances that i have found: Katarina's Shunpo, Nami's Ebb and Flow, Zyra's plants, Aphelios' Onslaught.

R - Dawning shadow

Ability full description ACTIVE: Senna reveals herself before firing two global beams of spectral light in the target direction, granting sight of the area briefly along its path. The center beam deals physical damage to enemy champions hit. The broad beam shields Senna and allied champions hit for 3 seconds. The broad beam also collects any Mist Wraiths in the way.

When to use:

You want to use this ability in teamfights where you can hit the most amount of champions. It has a huge cooldown, so try to save it when close to important objectives.

Since it's global, you can also use it to snipe any enemy who got out with 1 HP. You need good coordination / high map awareness.

General tips:

• This ability DOES NOT DAMAGE ANYTHING BESIDE CHAMPIONS. Don't try to steal objectives.
• The shield scales with total number of mists.
• You can R + Flash. The ability will always shoot from the original cast position. Senna will face towards the same original direction, but if you time it perfectly, she will actually face towards the blink direction (similar to Ezreal's Trueshot Barrage + Flash combo). So use it to trick enemies (very situational)

In this chapter I will show main combos that you should know to make this champion easier. Keep in mind that Senna is not a combo oriented champion and these are just simple things.

AA + Q - Basic trading/poking combo

You will use this combo A LOT in laning phase. It's an easy combo meant to deal decent damage and collect a mist from the enemy.

Q + AA - basic long range trading/poking combo

This is a variation of the first combo, it's meant to use your Q to its full potential by using it on minions and hit an enemy at max range, then follow up with the AA for the mist.

W + Q - Basic mid range pickup combo

This is an easy combo meant to catch opponents by casting W with an immediate Q for the slow. You can start hitting AAs after that

Ward + Q - Advanced long range pickup/finisher combo

This combo can be used with 2 purposes. First, you can use this combo to catch an enemy at max range with Q's slow, and you can also use it to kill an enemy out of range.

W + Ward + Q - Advanced long range pickup combo

This is also a combo to lock champions out of range. You W at max range, and then Ward+Q to slow them for an easy W hit.

W + Q + AA + R - Advanced mid range execute combo

This is the most damaging combo. It's used to burst down a single target (or more if your W roots multiple enemy champions). Try to use AAs every time you can for maximum damage. Be sure to time your R when the enemy is rooted, as they could use Flash or any mobility spell at the last second to dodge it.

In this chapter I will explain Senna's synergy with different classes of champions.

TANKS

By far Senna's best synegry. They are very forgiving so ranged enemies will not be as punishing as it looks. They also carry a lot of CC abilities so they can peel Senna in case of assassins or bad early trades. Their high resistances make Senna's healing more effective.

FIGHTERS

Also a really good synergy. they usually have great built-in sustain so ranged enemies are not a problem either. Their all-in is better compared to tanks but they struggle to get on top of the enemy botlane.

MAGES

Overall an effective synergy. They can keep up with the range of the enemy botlane. They have a decent early game but without a lot of kill pressure.

SUPPORTS

Also a solid defensive option. they are made to help other teammates so there's no adaptaion problems. And it may doesn't look like, but supports with full wave income can be very scary opponents. You will not have a lot of damage in the early game, but you have will have great teamfight potential.

MARKSMEN

Terrible synergy. They are meant to deal DPS and have no tools to help teammates. If you want to play alongside a marksmen, play support.

ASSASSINS

By far the worst synergy for Senna. They get destroyed by a ranged botlane, they have no tools to help teammates, and they have really different objectives compared to Senna. Never pair these 2 together

This is a Tier list of Senna's best Fasting duos. It is all in order, meaning that if a champions is above another in the same category, it is better in my opinion. I will now explain every tier:

S - Best

Best champions for Fasting Senna. Conformed by champions with good utility, damage, and tankiness and some specials interactions. If you want to climb with someone playing Fasting, you should start learning at least 1 of these champions.

A - Good

Still really strong picks, but not as good as the first tier. This champions are still an amazing pair with Senna but they might have a problem or two keeping them out of the "Best" tier, like not having enough peel, not having a good wave management or struggling against a double ranged botlane.

B - Average

As the name says, just average picks. The synergy is there, but it's nothing amazing. Some of this champions may feel outclassed by other above them, or they have some problems that are too noticeable to place them in a tier from above. I don't recommend trying to learn a champion from this list, but they're playable if you already now the champs.

C - Below Average

Niche picks. They work but with a lot of problems. Should be saved for specific situations or if you find the champions fun to play.

It's finally here!

Sorry for taking so long, but i wanted to make it right (It has gotten like 3 mayor overhauls before the actual release, lol). Right now (13.9) it's only for Support Senna, but i'm still working on ADC and Fasting. (13.10 UPDATE: a couple of hours after the update of this guide, i will drop the ADC matchups)

I have a Changelog in which i explain my future plans each update, so be sure to check that if you have any questions.

Anyways, enjoy! Click the text below to access it.

TheMistCollector's Senna Matchups Sheet

THIS SECTION NEEDS A HEAVY REWORK, PLEASE IGNORE THE SPECIFIC BUILD ITEMS AT THE START AND ONLY FOCUS ON "GENERAL ITEMS" ONWARDS.

In this chapter I will talk about every item viable on Senna. I will sort them by specific builds (items that you only buy on said build, as well as their core items), and general items (items that can be bought situiationally across multiple builds). Additionally, i will cover some other popular (but not necessarily good) ones.

Crit Build:

Core items:

Kraken Slayer - AD scaling True Damage, insane AS.

This item, alongside Guinsoo's Rageblade, is absurd in terms of damage. The AS and AD that it gives is amazing for the 2 item synergy. Additionally, it makes Absolution's free AD even more valuable because of the AD scaling true damage every 3 AAs. (This build does not need Manamune since it's primary focus are AAs). Build this as your first item every game.

Guinsoo's Rageblade - High AS, special interaction.

This item is the perfect combo for Kraken Slayer, It has a lot of AS, which means more True damage procs and more Qs (that is even more kraken procs because Q is basically a free AA). Additionally, Guinsoo's passive makes AD even more valuable because of Absolution's free on-hit damage, that gets doubled every third AA. As you can see, this Double Item powerspike is absolutely insane, it boosts Senna's damage by a giant amount (It also now proc Wit's End magic damage, even better). Build it every game.

Hybrid Build:

Core items:

Locket of the Iron Solari - High resistances, underrated passive/active.

This is a great tank item. it's really cheap and it makes you surprisingly tanky. The aura, although unnoticeable, it's always there making your teammates just a little bit more tankier. The active is kind of insane, and because it also affects you, that's another extra tankiness. Another important part about this item (and also the reason double resistances shards and Fleet Footwork are so valuable when playing support, is that the early tankiness is a great way to stack Mists consistently. It allows you to go more "kamikaze" than you normally would (remember, Senna has the lowest base HP in the game), both helping to apply pressure in the lane and scaling. Senna doesn't need to push an early lead through damage or zoning the enemy botlane like a Xerath, she just needs to hit her targets constantly, and early tankiness works the best. Build this as your first item as support as default.

Lethality Build:

Core items:

Youmuu's Ghostblade - Insane stats.

If you want damage, this is the best Lethality Mythic choice. Because of their lower stats, you only build Duskblade of Draktharr for the invis, and you only buy Eclipse for the shield, so Youmuus is the item with the best stats. Build this every game.

Manamune - High AD and Mana.

This is THE item for farming Senna. She synergizes very good with high AD and she has really high ability mana costs. Manamune allow Senna to be this damage/healing monster. Build this every game as farming Senna.

Situational items:

Axiomic Arc - Standar Lethality

axiomic arc

Best standar lethality item, as you can't use Prowler's Claw. Build this after you cores if you need more lethality.

Edge of Night - Vs. Skillshots(and more)

This item seems like a weaker version of Rapid Firecannon for Senna, butt it can be good against specific things, such as flank mages. If you're unsure wether you build this or RFC, stick with the latter. Build this as ADC against champs like Evelynn or (assassin) Ahri, who can sneak in ignoring your range advantage and have some sort of deadly skillshot after your core items (4th item only, after that lethality is not that good to buy.

Tank Build:

Core items:

Radiant Virtue - Highest HP item

Heartsteel's replacement. Old build used to be too niche and even in dream scenarios, its cost was still too high. This version of the tank build with Radiant Virtue is much cheaper, is playable in more scenarios and brings even more team utility. Ult cooldown is not that big of a problem as people say it is (just look at Shen), and the fact that is global is also not much of an issue since using a cross-map ult by default means that you're trading teamfight power for a skirmish. Build this as your first item as support as default.

Spear of Shojin - Standar HP + AD item. Special interaction.

I'm still not sure if this item will be considerable at all once the BC bug gets fixed, but for now i'm gonna recommend it. The item has the perfect stats that Tank Senna wants (AD, HP, conditional MS), and it also has an amazing interaction with her. Spear of Shojin has AD scaling AH in one of its passives. With Senna, this means infinitely scaling AH. Build this item as support right after cores if you don't need Chempunk Chainsword

General items:

Black Mist Scythe - AD poke starter

This is the only starter support item usable by Senna. The small AD helps with poking a little bit harder while having a little more extra healing. Build this as your starter item every match when playing Supp/Fasting

Boots of Swiftness - Standar.

Situational boots when MS will make you survive more than standar resistance boots. Either the enemy team has a lot of skillshots, or they're very melee with not a lot of ways to get on top of you. Build these boots when the extra MS will outvalue either Plated Steelcaps or Mercury's Treads survivality.

Plated Steelcaps - Vs. Physical damage or heavy AAs.

These boots should be considered your "default". It will practically always have value inside of SoloQ, specially in the botlane. Champs like Zed, Viego, Jax, Draven Pantheon get destroyed with these boots early on. Build these boots against Heavy AD/Auto attackers.

Mercury's Treads - Vs. Magic damage or heavy CC.

These boots are great if built in the correct match, it offers a lot of resistance against AP champions, or heavy CC (example of champions that get countered by these boots: Mordekaiser, Morgana, Malzahar, Ziggs, Leona). Build these boots against Heavy AP/CC.

Berserker's Greaves

After 13.4 AS ratio buff i believe these boots are viable on Senna. They are not as amazing to drop Swifties/Plated/Mercs completely, but it is good to consider them. Build this item when you want to have more DPS and/or you don't need any of the defensive boots.

Stormrazor - Good stats with insane AD scaling effect.

Even though this item is meant to be a rush, and its quite good at that, for Senna this is an amazing item after your cores because of its AD scaling. No matter if you're building Lethality or DPS, if you build this item in mid-late game it will hit like a truck, on top of the burst MS. Build this item after your cores if you need more damage.

Rapid Firecannon - Vs. Gap closers or deadly skillshots, special interactions.

This item works really good on Senna. The extra range helps with early survivability and it also helps to proc your Piercing Darkness slow from a long distance. This item shines with Senna's special interaction with it: Q range and hitbox gets bigger (since they scale with AA range), and you can AA+Q combo with one RFC charge (bug? either way it has been here since Senna's release, so almost 0% chance it gets "fixed"). Build this item as any role after your core items when you need the extra range, for example because of survivality (like vs. mages or champs that can easily close the gap). It also works great for support when you don't need any other damage or tank item, since you increase your catch potential by making your Q slow range bigger.

Blade of the ruined king - Vs. tanks.

Although i don't normally recommend Lifesteal/Omnivamp items, Botrk is just busted. You will shred tanks and get access to extra utility with the super low CD slow. It also synergizes great with the crit build, since it's mostly on-hit. It's not recommended to build it in lethality build same as Wit's End since you will not make a lot of use of the passive extra damage. Build this item as any role (except Lethality) if you need to deal with tanks. You can build this right after mythic as Warden support, or after core items as crit ADC.

Runaan's Hurricane - Great teamfight potential, special interaction.

This is a great item on Senna. Because of her long range, it's super easy to keep firing bolts and poke the enemy team down before they can fight. This item shines with Senna's special interaction with it: Since bolts counts as AAs, they each reduce Q CD by 1 additional second (up to 3 seconds per auto attack). This helps her to deal a lot of extra damge, as well as healing a lot of extra HP. Build this after you core items in matches where you have a great range advantage while teamfighting.

Phantom Dancer - Runaan's Hurricane alternative.

Alternative early Zeal item where Runaan's Hurricane will not be as efficient (You don't have a great range advantage, the enemy team will not be that close together in teamfights, etc). Build this after your core items in matches where you want a Zeal item, but Runaan's Hurricane cannot be used.

Wit's End - Insane survivability, cheap and good DPS.

Adapting to the meta, Senna is surprisingly a good Wit's End user. This item is really broken, it grants a lot of hybrid damage, movement speed and basically free magic resist. Build this after cores if you want MR while not losing out on DPS

Lord Dominik's Regards - Vs. Armor.

This item really helps with tanks, and it's just a generally good late build (Item is broken. everyone is running with 90+ armor and it is overbuffed. last check: 13.18). Build this item as any role if you need to deal with tanks or in the lategame for extra damage against any team.

Mortal Reminder - Vs. Healers.

Standar anti-heal item, try to never build this if you're not playing support. Build this item when against at least 1 Healer (example of champions: Dr. Mundo, Viego, Yone, Samira, Soraka.) You can build this right after mythic if needed.

Immortal Shieldbow

Decent item if you need survivality and your team can't peel you properly. It's the best combination of a damage and defensive item. Build it if you want survivality but don't want to lose that much damage.

Guardian Angel - 1st option Vs. High AD damage

The standar marksmen defensive item, it helps a lot with AD assassins because of the armor and resurrect passive. Build this item as ADC/Fasting after your cores if your biggest threat is an AD champion(s) that keeps 100-0ing you.

Frozen Heart - Vs. AD

Great item when you need the extra survivality against AD champs yourself or as a way to peel your priority targets because of its aura effect. Built this in any role after your cores when you really need the extra tankiness against AD champions ( Master Yi, Yasuo and Yone). You can build this more freely as support since you don't care about not building a lot of damage if it means protecting your carries.

Maw of Malmortius - Vs. Magic damage.

Standar defensive item against magic damage. Build this as ADC/Fasting after your cores against a team with basically all magic damage or if there's an AP champion that keeps killing you.

Anathema's Chains - Vs. 1 enemy threat

Alternative defensive item for any role if there is only 1 scary threat in the enemy team. It works great if you've built other defensive items as it only grants health. Build is in any role after cores if you need to stop 1 big threat on the enemy team, either to survive yourself or to protect your carries.

Knight's Vow - Supportive option for specific peel

Great item for Support (Tank and Hybrid only) Senna if you want to fully play around peeling a carry.

Spirit Vissage - Vs. AP

This is a great item against AP champions. It provides with A LOT of MR, plus some nice extra healing to survive almost anything. Build this as any role after your cores when you really need the extra tankiness against AP champions ( Akali, Ekko, Fizz). Although it does not have an aura effect like Frozen Heart, it's still good to build it as support in the same scenarios.

Mercurial Scimitar - Vs. Heavy/Undodgeable CC

Standar Marksmen item against Hard/Undodgeable CC. Build this item as ADC/Fasting if the enemy team has a deadly CC (example of champions: Same as Cleanse) as 5th/6th item depending on the build.

Zhonya's Hourglass - 2nd option Vs. High AD damage

This is an alternative to Guardian Angel. It's a little tricky to explain when to take one over the other, but the first thing i would consider is wether i can use the active before i get killed. If the enemy team's AD damage threat is really hard to react (example: Shadow Assassin Kayn), or if they have a lot of CC, i wouldn't recommend Zhonyas. Build this as a late purchase as ADC/Fasting against AD damage if it's possible to use the active before dying.

Mikael's Blessing - vs. enemy CCs (peeler version).

If your team really needs it, you can build it.

Vigilant Wardstone - Standar Supp

This is a must buy if you are the support item in your team. It solves the problem of always carrying a pair of Control Wards in your inventory, with nice stats (+ mythic passive). Also, the extra wards passive (in both inventory and map) is extremely valuable. Build this as 6th item in every Supp/Fasting match, you can also build it 5th if you can afford it before your complete situational item (like sitting on a Executioner's Calling while building it.

Elixir of Wrath - Standar.

This is the standar marksman Elixir, it gives a lot of AD, and basically free sustain because you don't need more gold at that point of the match, so that doesn't matter. Buy this item after your full build as a standar.

Elixir of Iron - Additional defense.

This elixir is good if there is still a champion in the enemy team who can kill you like nothing, also the additional tenacity is a nice bonus. Buy this item after your full build if you keep getting one shotted.

Popular items:

Eclipse

You're not using the shield enough to justify this buy. You will play for poke when building Lethality and Youmuu's Ghostblade is the better choice for that. Never build this item.

Galeforce

Passing up Kraken Slayer or Youmuu's Ghostblade for this item is simply not worth it. Never build this item.

Moonstone Renewer + Staff of Flowing Water

You heal for basically the same with any other build, except that you deal almost no damage and gets one shotted. Never buy these items.

Ionian Boots of Lucidity

Same as Berserker's Greaves. Never build this item.

Iceborn Gauntlet

This item is no longer a good purchase for Senna, as she already has a consistent slow on her Q, buying another one is not worth it. 12.22 UPDATE: It now builds out of Sheen, it's way worse now. Never build this item.

Silvermere Dawn

Mercurial Scimitar is just better. It gives better stats and it has a slightly better active. Never build this item.

Sheen items

Any Sheen item is bad on Senna. They all scale with Base AD, and she's stuck with 50 throughout the whole match, because of her passive. Buying a Sheen item is significantly weaker on Senna compared to every other champion. Never build a Sheen item.

Dead man's plate

Some people build this item as an alternative to Black Cleaver when the enemy team doesn't have enough armor. It looks like a good idea, but the item is generally trash, and it additionally scales with Base AD, same deal as Sheen items. Never buy this item.

Steel Shoulderguards

Some people start with this item in bad matchups, like a normal enchanter should do, but because Senna doesn't want to kill minions because she gets reduced mist spawn chance, buying this item weakens Senna as a whole. Never build this item.

Support Crit Build

The build is crazy expensive, expect to start dealing damage at +25 minutes into the match, and most matches are already decided by that point. Also, your team does not need another squishy DPS carry. Never go for this build.

Divine Sunderer

In this patch (12.13) Divine Sunderer was changed so it scales with Base AD, and how I explained in the Sheen section, Senna has terrible base AD, that does not increase with level. I know that the Sheen section should naturally include Sunderer already, but i wanted to make a distinction since before this patch it could be built because of its different scaling. Never build this item.

Support Manamune

As i've noted in quite a lot of other chapters, Senna does not need Manamune's high mana because the support item already gives enough of it. If you build it because of the high AD, you're better with something like Umbral Glaive or Serpent's Fang. Never go for this item as support

Guinsoo's Rageblade

After 13.18 Senna buffs, this item is useless. The only reason it was built was to justify building early crit because otherwhise her crit modifier made it too bad of a purchase. Now that she doesn't have reduced crit damage, building early crit is fine. Never build this.