Yo
I wrote this guide because I hate when people play terribly with my favourite champion maybe even not because of their noobishness, but simply due to lack of knowledge about basic and most important things for yi. Other reason is that in my opinion the best rated master yi guide on mobafire [DEWO's guide] is just not the best option for him.
Also I wrote this guide mainly for people that just love to dominate.

So why would you follow my guide, not the other ones? Every guide maker thinks he is a pro.
Here you've got proof, that I know what I am talking about.

Special thanks to Noraa and DEWO.

At this point I need to apologize for all langauage mistakes I did/will do.
Sorry, you will have to spend some time if you want to read all, I hope you won't regret it.

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Introduction

What is Master Yi? I can honestly say, that well built he is the biggest dps on League of Legends fields. He is extremely fast, only rammus can compete.
A great champion to push lanes and destroy turrets, and a carry for the team.

Pros:

+unfair dmg
+super fast
+good carry

Cons:

-squishy
-no stun/slow etc
-vulnerable to stuns and other disables
-that sneaky bastards only wait for the worst moment to surrender :D

Play Video

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Abilities

Double Strike
Master Yi strikes twice every 7th attack.

There are many champions with better passives, but let's figure out how we can use this one. In early game, it can be used to deal surprisingly big dmg, attack minions so your passive icon info comes to "your next attack will double strike" (or sth like this) come closer activate wuju style and hit enemy. You can also alpha strike first and then double strike, effect will be even better, but do it only when u are 100% sure you will survive it.

DEWO wrote

Well that would be nice, BUT only first strike can crit, so you can deal dmg as from 3 normal attack mostly.


Alpha Strike
Master Yi leaps across the battlefield striking up to 4 enemies, dealing 100 / 150 / 200 / 250 / 300 (+100% of ability power) magic damage to each enemy with a 20 / 30 / 40 / 50 / 60% chance to deal 400 bonus magic damage to minions.
Cooldown - 18/16/14/12/10 seconds
Cost - 80/90/100/110/120 Mana
Range - 600

This skill has second priority, mainly because cooldown is lowered after each point in it, and you want to jump to other enemies often.
Don't spamm it early game or even use to harass, it eats too much mana, use it only when enemies/minions are under your tower.
Good to know:
It's random who will you strike with it, except for that you will surely strike the target you clicked on (unless he flashes, teleports etc.). So you teleport to clicked target, if it will die, you appear in the same place you were while activating alpha strike.

Flash breaks it, skills like kassadin's riftwalk or shaco's deceive too, but you follow champions when for example: tryndamare is spinning through wall, tristana jumps, nidalee jumps. Now after one of last patches your alpha strike follows flashes and other teleports (yay :D)

You can also hack walls by jumping on a minion on the other side of the wall (that minion needs to be seen).
Play Video
Also, you don't vanish from battlefield for animation time. It's like you stand invisible in the place you started alpha striking from, so better don't try dodging Ashe's crystal arrow with it. Every non marking skill shot can hit you if aimed in that place.
Now you can, it can be used as a dodge spell, I don't know yet if it works just as shaco's ultimate, with dodging turret hits or karthus ulti, etc.


Meditate
Master Yi channels, restoring 140 / 280 / 420 / 560 / 700 (+165% of ability power) health over 5 seconds. While channeling, Master Yi gains 100 / 150 / 200 / 250 / 300 armor and magic resistance.
Cooldown - 35 seconds
Cost - 70/85/100/115/130 Mana
Range - Self

Most games we will leave it and upgrade only if there is nothing other to upgrade, other abilities are more useful, but let's see what can we do with it.
At low lvls of this spell heal is super ****py, but you gain really huge amount of armor and magic resistance. So it's not actually heal, it's a SPELLBLOCK.
If you are facing Karthus, you HAVE TO give 1 point in it on lvl 4 instead of alpha strike. It saved me so many times that I can't remember. You just ran with 100 hp and you see that red noob thing above your head? Meditate! It will recover about 40 hp and his ulti will deal about 3 times less dmg than it would normally do. You will survive 90% of such situations.
When do we put 1 point in it? When you face enemies that deal massive amount of dmg with range abilities that has to fly to you slowly or just do dmg after time. So Karthus, nunu's ice ball, zilean's bomb, vladimir's ultimate etc.


Wuju Style - Master Yi becomes skilled in the art of Wuju, passively increasing the power of his physical attacks. Activating Wuju Style doubles the passive bonus damage for a short time, but the passive bonus is temporarily removed after the effect wears off.

Passive: Increases physical damage by 15/20/25/30/35.
Active: Master Yi can activate this ability to double its effectiveness for 10 seconds, but this removes the passive bonus until Wuju Style becomes available again.
Cooldown - 25 seconds
Cost - 40 Mana
Range - Self

About this 1 it has all been said. It is your most important ability except for ultimate, after upgrading it on lvl 1 your crit deals 190 dmg. Nice? Freaking awesome!!! :p


Highlander - Master Yi moves with unparalleled agility, temporarily increasing Master Yi's movement and attack speeds as well as making him immune to all slowing effects. Additionally, killing a Champion refreshes all of Master Yi's cooldowns.
Increases Master Yi's movement speed by 40% and Attack Speed by 40/60/80%, and he becomes immune to all slowing effects for 6/9/12 seconds. Additionally, killing a champion refreshes all of Master Yi's cooldowns, and scoring an assist reduce the cooldowns by half.
Cooldown - 75 seconds
Cost - 120/120/120 Mana
Range - Self

This is what makes yi a yi, you can't do quadra and penta kills without it. It's just unfair combined with youmu and ghost.
Good to know:
So you used R and E abilities and you killed a champion and your cooldowns are refreshed. In this moment, you get bonus dmg from both, wuju's passive and active, because it is activated and it is also ready to use. So when you go to another champion to kill him don't activate E again just after you killed previous one. Wait until active ends and then use it again. Same with highlander, don't use it all the time you see it's ready to cast, thx to this you will run fast longer, often meaning to get to that last champ for penta kill or not.


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Runes and Masteries

So let's start with masteries. It's not so important if you want to build it in some other way, important is to have those 21 in attack. Changed:I go with 21/8/1 now, as I don't feel that few % of experience as useful as some defense.
Point in 15% magic pen to boost alpha strike, not a must have.
That's it.

Edit:I've checked 0/21/9 masteries and it was a failure. You lack dmg until really really late game.

FINAL RUNES
After deep research, I've decided to change rune setup and here it is:
9x Greater Mark of Critical Chance -> still the same
9x Greater Seal of Critical Chance -> still the same
9x Greater Glyph of Magic Resist -> new
3x Greater quintessence of desolation -> new


This give you 12% crit chance, 10 armor penetration and 13 magic resist.
So you loose 8% crit for 10 ArP and 13 MR, what really sounds nice.

With masteries your total ArP is 16, what is exactly the average base armor in league of legends. Here you can deal so much dmg that Le Blanc's jaw will make a hole in the ground.
Why? Wait till double strike will be on and if enemy comes into alpha strike range, you activate wuju, alpha strike and then double strike. Let's say it's lvl 2: you have 1 point in wuju and 1 in alpha. Your actual ad is 80, after activating wuju it's 95. Alpha strike-> 100 dmg - MR ~90 dmg, now double strike = 190, that's 280 in total. Also if you crit, you deal additional 95 dmg so it's 375 dmg on lvl 2!!! That's how you open a fight, if your lanemate has a stun it's gg, thx for feed. Play Video

OLD = BAD
So runes now. All in crit chance. It gives you 20% crit chance. With 2% from masteries and 8% from gloves at lvl 1 you have 30% critical chance. It really makes people miscalculate their chances. For example: lvl 1, fiddlestick chasing my lane mate and just understimating/forgetting about me. He gets 1 hit for 1/3 of his total health. He just didn't notice that. So he gets the second hit. Now he is like wtf has happened to me? But I'm on his way to his safe lovely turret. 1/2 more hits and he is dead. I'm faster (biggest base move speed and ghost) and he had to run next to me. No chance for him. Rest in peace.

Also it's not only early game good. With youmu and infinity and masteries u have 37% crit chance in mid/late game. Not much really. Most games won't be so long so you can build phantom dancer to have 67% crit. So runes IE youmu and masteries gives u lovely 57% crit chance. You can also boost it with green elixir if you have money left and u feel a need.

Why no crit dmg? "It is good late game", that is the only positive argument I met. When you crit often you deal more dmg than criting rare but stronger. This may not convince you so let's give another 1. I don't know with IE and it + 10% masteries you can get it to 300% crit?
Then it's 40% crit dmg more. When u have youmu + IE as only dmg items u crit with my build for 691. Let's do some math.
260% <-> 691
300% <-> x
26x=691*30
x=797
U get a bit over 100 dmg more with every crit, but u crit every 3rd attack instead of above every 2nd. In late game such dmg boost doesn't really matter, u are terrible monster for your enemies anyway.

Armor penetration is better in my opinion than crit dmg, but still much worse than crit chance.
DEWO wrote Well crit chance makes much more difference early game, however double strike + wuju style combo works better here. You will have armor penetration from youmu and stark's fervor.
If you still wanna stick to armor pen after what I said then ok, just buy crit chance runes and later 1 time try it and see what is better.



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Items step by step with gameplay explanation

You start with and 2 x (if you don't have crit chance runes or you are just stubborn and you go with armor pen - start with long sword and 1 health pot). You can go either lane or mid, however your team probably will prefer someone other to go mid, like ezreal, karthus, heimer etc. Anyway you always have to play DEFENSIVELY. What I mean is, don't push lane, let enemies come closer to your turret, it's much safer. You are unlikely to be ganked and you can follow secret tactics in peace. First rule is to last hit minions. It's nothing new, you need to do that with every champion. Good part is that you do that better because you have more dmg than others. So DON'T auto attack full healthed minions. Following this will bring fight nearer to your tower.

So what are those secret tactics I mentioned?
-You can last hit melee minion after 2 turret shots
-You can last hit caster minion after 1 turret shot (this one is not working if u are lvl 1)

RULE: don't die, it's better to not die and not kill than to kill and die.

Main Goal: Survive without dying.
Play Video
On this video we had very hard lane, nunu harassed us so we were loosing gold (we couldn't last hit majority minions). But we SURVIVED, and later I will show you what happened next in this game.

So later buy items in order like in item build.

For lazy people: When you have 1150 gold you can afford upgrading your gloves and buying boots + scepter. If you have 1980, you can add to this list 2 long swords, you shouldn't stay in lane without bluepilling any longer than this (never).

Worth knowing:When u have
You can feel free to go jungle without any health pots and need to bluepill. Don't do dragon yet, start killing neutral minions with alpha strike. Golem and Lizard should do dmg equal to your lifesteal.
But go jungle only if you are sure that your lane mate can handle lane alone.

So if you decide to go jungle, you should choose neutral minions that are nearer to the lane that is likely to be an easy gank. If there really is no such lane, start with 2 golems and just clear all jungle on your side of the map, rather don't go to enemy jungle, it's too risky. Yeah you can win 1 vs 1 but they get support really fast there. So then bluepill and buy something or go help in lane (ganking/pushing/holding turret).

Tip:Golem and Lizard respawn 6 minutes after they are killed, it's not important to always have the buffs but they help a lot. Slow is nice but nobody can run away anyway, so it is better to get blue buff to spamm alpha strike.

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Our

CORE

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In almost every dps champion build writer says sth like "in this moment u can win every 1 vs 1" or "now u can take down anything". Well, that's not true. They can't 1 vs 1 with you. At this moment you need to be careful with towerdiving, cause you really will feel strong. Now you should just take a look at map and go kill the easiest target or go dragon if you feel unlikely to kill atm. With little core you are not loosing any health while fighting dragon, be careful however because it's very often warded.

Why 2 scepters? Trust me and try it. This will give better explanation. Often with 100 hp you can kill full healthed champion(s).

Tip:At this point if you are out of health and mana + you have not enough money for further upgrades, you can kill golem so you will replenish both - health and mana.
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How does deadly combo look like?

God mode on:
( )+ + +
don't change the order, you should activate all in pretty the same time however
now click the enemy champion and watch :p
warning! don't use alpha strike to initiate, save it cause you will probably need it in few seconds, if they flash/teleport-> alpha strike to them, stun-> cleanse and same thing.
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Nextly let's improve our boots, I placed boots in build, which I use almost all the time lastly.
If they have stuns, many casters, slows, taunts it's the best option since it minimalize your biggest weakness - vulnerability to all kind of CC.
You can also buy , or which in some games are useful, or if you really think it will work fine for you. Find boots that suits you the best.
Lastly I found very nice to buy items that except for main usage give you some armor/magic res, so if u have marc threads and wit's end, it's already pretty something!/same with ninja tabi + madreds

Now, if you are not forced to buy something defensive, go for something with inside, preferably .
If they have 3 or more super beefy champions, buy instead, starting of course with .
If they have 0 or 1 caster, which can't kill you with his burst(what happens really rarely, but yeah, happens) you don't need more MR so go for .
If they have some dodge champion that can be a serious threat, buy
In other situations is a much better choice.

[if you need something defensive you can buy it now too, if not:]
Go for starting with




DEWO wrote

********. Sorry Dewo but really, there is nobody fighting you (unless you play with total newbies?), there are no 1 vs 1, if someone sees a mad butcher with giant sword rushing on him he ****s his pants and runs away. So you have to run to him, strike, then again run to him and so over and over. AS is pointless then, it's only better for farming, but you are too busy with killing to farm. So here we have bigger dmg and movement speed while we have less AS. We catch up to enemies faster, we hit them harder, AS is not working.
Play Video
I hadn't got lvl advantage, I also hadn't got money advantage (yeah I had more kills already but I lacked money from nunu harrassment and Miss Fortune was middle lane so she earned more money that I did). This vid shows well what I meant by "catching up and striking".

Other argument against your theory: let's say we have AS boots, stark's and phantom built.
Let's say we have attack speed = 2 now (but we even haven't got that much). So enemy is lagging and he is standing in 1 place not moving. We double strike every 7 hits so it gives us double strike every 3,5 seconds. In my build we kill non tanky champions in 4-5 hits, why would u wait for double strike? We will have here highlander on lvl 2 so it gives 60% AS, youmu gives 50%, you don't need to strike faster. I strike for 691 atm, and you?




I changed my mind about the idea of having little and big core, I made 1 core instead and the many possibilities of different item paths later made the build more flexible




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Warning! You always keep behind your teammates waiting for battle initiation. When you see someone from your team has already got focused and they used most of their stuns and disables, that's the moment you finish sharpening ur blade and do your butcher's job. In teamfight enemies stand and throw their damaging things into your teammate. They stand in 1 place! It takes about 1-1,5 second to kill tristana or other squishy hero. So now it's obvious what to do. Time for multikills. (Chase & kill)x 2/3/4/5
Play Video
So I had that bad beginning with nunu, but after I bought youmu it didn't really matter. (Sorry for lags)
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Some specific situations:
You lack magic resistance - lot of casters? Go banshee
Hint Evelynn can't stun you when u have banshee. It also doesn't allow twisted fate's ulti to reveal you, and it blocks karthus's, ezreal's and ashe's ulti.

They have well doing Jax or Sivir? Move it to slot nr 2, and use it when facing 1 of those 2.

Enemy team has Tryndamare? That will be gooooood.
Why? U can't kill him by that 6 seconds, so after he kills you he will have to run away (90% situations) or wait and die after you are revived.
It is often viable to sacrifice 1 item for it in other situations too.

on hard tanks

So funny! This one was DEWO's idea, good job :D lovely at creep waves and crowdy teamfights. Btw it's passive stacks (meaning if you have 5 tiamats, 250% dmg splashes, so if you crit for 1000 a creep, you deal 2500 dmg to everything around)

If you bought guardian angel, and you don't know if you want bloodthirster or phantom dancer for the last item, and you still lack survivability, it's a great choice which gives you almost all you need: damage, attack speed, some armor and tank killing power.

If they all have stuns, it is really good idea to combine it with cleanse (unless you die on burst dmg instantly (like Annie's combo) then banshee is better).
It is also a must against Malzahar/Warwick, because their ultimates do supress you, not stun. You can't remove supression with cleanse, but you can with this!
Btw it's super cheap - great item.

Bad ideas:

-want slow? go red buff (like they could run away anyways)
-want health? you picked wrong champion
-20 additional dmg for this price? kiddin?


If you survived the burst, you won. You kill casters with 3 hits so... how much mana will they loose? Totally not recommending.
After new patch, it's a great item! Why? 1. It costs 2000, just 350 more than B.F. Sword. It gives you 42 magic dmg each hit, which is only 3 dmg less than B.F. Sword(not counting crits) and it also gives 40% AS and 20-40 MR!!! All this for just 2k gold, awesome!

How to counter:
At first you should avoid people with thornmails, but when you just killed all non-thornmailed champs, to not have to run away, follow these tips.
There are 2 ways to counter thornmail:
-More lifesteal
-Magic resistance
I prefer the first method as you still maximize your dmg. Against heavy tanks it would be good to have that and , and instead of .
If you prefer the 2nd way you can go for .
Care: Sometimes this way is better, because:
-mainly tanks have thornmails -> they do not much dmg -> that little dmg loss is filled with huge hp regen and ls from 2 scepters (completely) -> you win

So let's end this match!
Play Video
How can full build look like?
-standard game (my favourite build :) )


-Godlike dmg (vs total noobs only)


-against non casters


-against super tanky teams
( / )

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Summoner Spells

+
Definitely the best option with yi

Without ghost, I guess I wouldn't play yi. The speed you achieve with combo is just so unfair that it totally devastates opponent's morale. It makes me feel like a God.
You get contol about situation, enemies can't run away, they can't fight with you too, so what can they do? Absolutely nothing!

Why cleanse? You don't want to pop up your ulti and be stunned do you?

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Additional stuff

Your worst possible lane enemy is Zilean. Definitely.

Nice lane mates to have: all with stuns, snares, slows, taunts.

Cleanse take out Exhaust, as well as (Teemo's) blind but not Ignite or Mordekaiser's ultimate.After last patch it does not take out exhaust anymore, only it's slow.

Feeded Galio + feeded yi > full 5 champion team. So you have pro Galio in your team, and you bought instead of bloodthirster. Galio taunts them to him... xD

In the worst possible moment while towerdiving, you will be exhausted.

No matter how far you are in the back, somehow you die in the front...

GOLDEN INFORMATION: There are turrets you know...

About Youmu Ghostblade
DEWO wrote:
Yep, why not? It has the same cooldown as Highlander! True, and this is your only point about youmu, but it gives you more champion killing power, what is your actual job, not farming.
I am laughing when someone says that. Same with ghost. "why ghost when i have my ulti already? :O"

As I promised Play Video It's not the final proof, I will upload just a pure pwnage soon, but just until that look at this one. You CAN'T do that without ghost and youmu!


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Funny Master Yi stuff : D
Chasing Master Yi
Don't chase - No tank

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DEWO's guide I was referring to.

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Tank Master Yi

Weird? Yeah but it works very well :D
Probably the best option here is
Dante Rebellion's Forbidden Style.

Very strong early and early/mid game. Later depending on how fed you are. Youmu at beginning gives you dmg and speed you need to win everything. After warmog you are unkillable but it takes long to kill fed tanks. After starks and atma is your dmg's big come back, and you can just do whatever you want with your enemies. Well, that's it. :D


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AP Master Yi

I haven't got much experience with it, you should check other guides if you want to have trusted AP build.
I think core build like this would be good:

I just copied it from another build, it's not mine.


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Summary

Deadly combo/God mode
( )+ + +
D + R + 1 + E click enemy and enjoy ;>

The result?


Important: This build allows you to be good even if your team is totally dominated. Some proof:You should be interested mainly in top right corner. My team had 31 kills in total, 25 from it were mine, and enemy team had even more -> 34 kills. We had one afk and that's why it was hard game for us.

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End

Thank you for spending your time reading this guide and don't forget to rate it! :p
If you want to help me improve this guide write some advices in comments, I am also opened to any kind of criticism :]

Be nice and have fun playing League of Legends!