Master Yi is a rather controversial champion. He has a terrible reputation to be an unstoppable late-game attack damage powerhouse, mowing teams down with attack speed and attack damage steroids. If you've played Master Yi as a beginner, you'll understand how powerful his late game can be. However, you'll also see how Master Yi's potential falls off a cliff as your opponents get better. Master Yi is rarely seen in ranked games, and nearly never seen in the competitive scene. AD Master Yi is way too squishy, and has way too much trouble early game to be of any use late game. That is why we build AP Yi. Building AP gives Yi sustainability, survivability, ranged harass capability, and overall, viability in high level play, and even in ranked games. Read on, and you'll appreciate the terrible power of AP Master Yi.
Pro's and Con's, AD vs AP
Here's a nice tl;dr for the introduction, and also a definitive comparison of AP vs AD Master Yi:
Master Yi: AD
Lots of sustained DPS.
Can chase down and kill squishy champions without escapes.
Destroys towers in seconds late game.
Can dominate any 1v1 fight.
Hard to catch and hard to kill (with lifesteal).
Rough early game, relies on a weak alpha strike for damage.
Extremely squishy, and no real sustainability without lifesteal.
Can run out of mana easily.
No AoE potential.
Gets destroyed by chain CC.
No lategame without a good early game.
AP Master Yi
Great AoE burst.
Mows down minions in seconds.
Alpha strike grants invulnerability.
Your meditate heals you faster than the spawning well.
Meditate also makes you invincible with bonus Armor and Magic Resist.
Amazing early game, and good transition into late game.
Hard to gank.
Can surprisingly outlane many popular AP mids, including Kassadin.
Low amount of sustained DPS.
Has difficulty destroying towers as fast as AD Yi.
Low ganking potential.
Reliant on getting a kill in a teamfight to allow you to snowball.
Overall, AP Yi still has tons of physical AND magic damage, can burst with AlphaStrike into a double hit(passive), or an Alpha Strike into a sheen or Lich Bane proc late game. AP Yi beats out AD Yi in tankiness (catalyst), in sustainability (with meditate), and AoE potential (800 damage Alpha Strikes FTW). Now onto the guide!
Before going into too much depth into items or runes, I first need to explain exactly how AP Yi is played. This is essential, because there are many nuances that need to be mastered, or else you'll make a complete fool of yourself playing Master Yi.
First, as AP Master Yi, don't be afraid to ask for mid lane. If your team already has an AP carry who wants mid, you should consider playing a different champion, and trying AP Yi next game.
Second, during the laning phase, mastering the use of Alpha Strike is essential for your victory. You don't Alpha Strike the champion, you alpha strike the minions. Alpha Strike places you next to whatever you targeted after the spell ends. If you target a champion, and that champion walks backwards into their tower before the spell ends, you'll end up standing right next to them, getting showered by tower hits. Which is not good. That's why you target the minions. Since it hits 4 targets, usually, you'll deal damage to the champion by targeting minions anyways. It keeps you at a safe distance away from the enemy champion and tower. It could also fetch you a couple of good minion kills, since Alpha Strike has a chance to instantly kill a minion you target. Don't use it too often though, because you'll not only run out of mana, but also push your lane and leave you open to ganks. There are some times when you DO want to target the champion, if you want to go in for a kill, you should Alpha Strike the champion, if you gank, you should Alpha Strike them too. Since it teleports you to the champion, it could even bring you across walls if they flash halfway through the animation. So basically, if you want to harass, target minions, if you want to kill, target champions. Easy-peasy.
*Note: When there are multiple targets around, you can notice that alpha strike takes a bit longer to finish casting. When you cast it, you turn into a yellow blur as you fly from enemy to enemy. During this casting phase, you are completely invincible. That means skillshots, targeted abilities, Karthus's ultimate, etc. will NOT affect you. Using this in teamfights allows you to "dodge" a lot of incoming damage.
*Another note: If you cast Alpha Strike, and your target for Alpha Strike dies before the spell finishes, you return to your original location. This can let you harass safely from your tower, if you so wish.
Thirdly, it's imperative that you master the use of Meditate. It's not just a useless skill for Master Yi, which many inexperienced players believe. It gives you a disgusting amount of armor and magic resist, and also heals you faster than your spawning well with enough AP built up. You go from 200 health to 2,000 health in seconds. This is the true sustaining power of AP Master Yi, in the lane, in the middle of teamfights, in a 1v1 waiting for your cooldowns, tanking towers, baron or dragon. Anything. Gonna get screwed over by Karthus, or anyone else with a global ult? Push W. It's an amazing skill, but only if you use it.
There are two paths you can take with Runes. You can take flat Armor Seals and Magic Resist per Level glyphs, giving you a lot more survivability. The problem with this, however, is that you'll be forced to start Doran's Ring, for the mana regen and AP. The other alternative is to take Mana Regen per Level Seals, and Flat AP glyphs, giving you a lot more early game punch in your Alpha Strike. If you choose to use this set of runes, you may start boots or Doran's Ring, depending on who you think you're going to lane against, and your personal preference. For Marks, take flat Magic Penetration, as they're the best choice for any AP champion, and for quints, take 1 flat HP quint, to push you well over 500 health at level 1, and 2 flat AP quints for some more damage on your Q. I suggest you try out your own rune combinations yourself, to suit your own playstyle.
With the new patch, AP champions may now place 21 points into offense, and gain significant bonuses. The mastery page I placed at the top of the guide is probably going to be standard for most AP champions, reaching magic penetration and Executioner in offense, and movement speed plus extended buff duration in utility. You shouldn't diverge too much for masteries, as I feel that this gives you the most benefits possible. If you've found a better alternative, please message me or contact me in a way, so I can mention it in this guide and give you acknowledgement.
Here comes the juicy part. Items.
The best starting item I prefer is a Doran's Ring. If you're playing blind pick, or you're in a hurry and you don't want to waste too much time at the start, just grab this nice, shiny blue ring. The magic of it is that it gives you mana regeneration, letting you harass often with your alpha strike, and also AP, which heals you with your Meditate skill, and deals damage on your Alpha Strike skill. If you want, you may also start with Boots and 3 HP potions, which, together with your naturally high movement speed, will let you dodge the skills of many champions such as Cassiopeia, Karthus, etc.
On your first trip back, definitely grab the basic, level 1 boots. The biggest mistake new plays make is buying a second tier item without first getting boots. Boots will save your life, grab you kills, and allow you to function efficiently on the battlefield. There's almost never a scenario when you'll have a built up item before your a pair of basic brown boots. If you can afford it, grab a catalyst with the boots, if you can't, then buy some HP pots and one or two wards, and get the catalyst on your next trip back. Catalysts are incredibly overpowered. Don't overlook the power of a catalyst, it's the best mid game item out there. Get it.
Next, you'll want to grab your Rod of Ages, and tier 2 boots. I highly recommend Mercury Treads, as it gives you magic resist, and also sweet tenacity. It's also one of the best items in the game. If you want, you may grab Sorcerer's Shoes instead, if you think it'll help you reel in the kills.
After your RoA, a good item choice is a sheen. It gives you good burst after your Alpha Strike, proc'ing off of your naturally high base attack damage values. You'll want to complete it to a Lich Bane, and then grab a needlessly Large rod for a Deathcap. Finishing off your build, grab a Frozen Heart, for cooldown reduction, crazy armor, a nice debuff aura, and tons and tons of mana. After that, feel free to drink as many elixers as you want.
Always start off with alpha strike, since you're playing Master Yi. As an AP champion, you should take mid lane. Don't be apprehensive, Master Yi is a better solo mid than you may think. Getting Wuju style at level 2 gives you the passive AD bonus that lets you last hit with ease. At level 3, you may grab meditate or Alpha Strike, depending on the situation. Either way is fine. Your ultimate goal with your skill leveling is to max out Alpha Strike first, then Meditate, then Wuju Style, and grabbing a point in your ultimate whenever possible, at levels 6, 11, and 16.
These two spells are pretty much staples for AP Master Yi. Flash is necessary no matter what champion you play, since, in a game that revolves around your positioning, allowing yourself to be repositioned instantly is the best you can get. Ignite is the finishing move that will get you all your early game kills, and can also be used to shut down champions that have a lot of lifesteal, spell vamp, or passive regeneration.
If you dislike ignite, you can take any one of these summoner spells, cleanse, for getting out of "sticky" situations (lol), exhaust for teamfights, or heal, for with its recent buffs, is decent in a 1v1 situation, and tactically useful too, since you can bait with it easily.
And that is the way to play Master Yi. In a couple of week's time, building AP Yi like such will become standard. This guide is here to educate, and I hope you all have success playing Master Yi the way I've shown you. I also hope you picked up facts and tidbits that you may not have been aware of when you read this guide. If you enjoyed it, or completely rape your next game as AP Master Yi, feel free to drop a comment, or give a vote of support. If you've had some nice matches that you want to share with the community, send me a screenshot and I won't hesitate to add it to the guide.
gl hf, LoL'ers