Welcome to my guide for Master Yi, hope you read and can learn something n_n Multiple builds up if you want to try some different styles / do well against different teams and find something right for you. 5th one is AP solotop or mid.

Master Yi is an excellent and fun AD carry who can tear enemies to shreds, massacre minion waves and turn towers to dust.

If you're looking for a fun / screw around build take a look at my other build :D http://www.mobafire.com/league-of-legends/build/master-on-hit-125160

Pros

Good farmer, Alpha strike can occasionally one-shot minions even at low levels
Good pusher
High attack speed
High movement speed
Insane ultimate


Cons

Squishy
Often a priority disable target (CLEANSE DAT ****)
Mana issues
No CC ability

I use a bit of a hybrid AD dps build aiming for all primary runes which works well for me.
Greater Mark of FurorExcellent for mid - late game, extra 20% damage on most hits.

OR
Greater Mark of Desolation Without these runes your early game is a bit harder, but i feel the extra damage from the Furor runes can make up for it.
Greater Seal of Vitality Personal preference, I think the extra health is good on Yi as he is fairly squishy.
Greater Glyph of Focus A little extra CDR on Yi can help with his harassing and at times his survivability.
Greater Quintessence of Desolation Best quint in my opinion, Possibly swap out with crit damage% runes if you're using the marks, though it'll make earlygame harder again.

Greater Seal of Malice +Greater Glyph of Malice
Mainly for early game. Crits at low levels can be devastating; add double strike to that and you can outright destroy someone.

Full AD runes also possible but not recommended.

Double Strike This has got to be one of the best auto attack passives in the game, every 7th attack you get a two for one strike. This is a very important part of Yi's play, especially early game. When engaging an enemy you should always try to head in with double strike up for that extra burst and so you'll have it ready again sooner.

Protip: When you have a jungler on your team, Go into the jungle with them and hit the jungle mobs -Don't kill them though- until your double strike is up, then proceed to whichever lane you are in. An alternative to that is to get your lane partner to leash the golems and run back and forth behind the trees at bottom/top lane while you hit them alternating so you dont kill either. Your first attack on an enemy at level 1 will be an alpha strike / double strike combination which will half health or more just about anyone. Excellent strategy for firstblood. Ashe is a really good partner for 1shotting firstblood with her passive (Yes Yi + Ashe bottom, being a metagame tryhard is for ******s.)

Alpha Strike This is Yi's Jack-of-all-trades ability; It can be used for harassing, farming, chasing and escaping -- if used to perfection it can be gamebreaking. Mastering this ability is one of the keys to playing Yi well.

Early game it is excellent for harassing, multiple successive hits from it can really bring an enemies health down. It also offers one of, if not the best early game combos in the whole game and you can do it at level 1! - Get double strike up and then alpha strike onto an enemy and you will get an instant 3 hits on them: this can do more than half health to many enemies. This combo should be used as much as possible when attacking as it remains very destructive throughout a game. Another good trick can make alpha strike a miniature version of LeBlanc'sDistortion ability. If you alpha strike a minion very close to death which dies before alpha strike's animation finishes, you will teleport back to your original position.



Alpha strike has a 20 / 30 / 40 / 50 / 60% chance to deal 400 bonus magic damage to minions. This is such a great ability for farming due to this, it's nearly the same as having aMadred's Razors and it can hit 4 targets at once. This is why I like to make it one of my first skills to level up.


When chasing enemies, if they're a little too far to catch alpha strike can get you on top of them and your movement speed and cleanse can keep you on them until they're dead. Alpha strike can also make enemies escape moves useless if you time it well; See a Tryndamere spin through a wall to safety? Not if you alpha strike just before he does it and follow him through. Sometimes you can luck out and guess when an enemy is going to flash and still be on top of them afterwards as well.

You can make some really great escapes and survive with Alpha strike as well. Example, you're trapped in a bad spot and cant run out of the way of Lux's ulti but you see a minion or enemy to the side so you alpha strike onto them. If you have good reaction time you can even use it to get out of Ashe's Crystal Arrow and other similar Ulti's. Another good way of escaping is to have wards in the jungle that can see minions, then you can alpha strike through the wall and keep running.

Meditate This is an underrated and often misused ability. You always want this to be ready to use before going on the offense as it can really change the outcome of battles. The heal isn't any good as AD, but its mainly the resists that make this such a great ability. On so many occasions can this get you out of tough situations if Alpha strike can't: Ashe arrows, Lux ultis, Ezreal ultis, Karthus ultis, etc, etc.. It can also be useful against very high burst damage characters like Veigar, Ryze, Leblanc - You can meditate through their initial burst and then lay into them while their abilities are on cooldown.
Yi is often a priority target in team fights as well, so sometimes if you're most likely going to die you can use meditate to benefit your team. If the enemies lay into you while you meditate you might distract them long enough for your team to kill off a few, get a good position, or escape if they need to.

--NOTE-- When against an enemy team with a Karthus, Caitlyn, etc. You HAVE to pick up a point in meditate at level 3 or 4 as they can save you from their ultimates.
Wuju Style Not much to say here, passive attack damage boost on an high attack speed and damage character.. awesome. When maxed and activated the +70 attack damage is like having a 7th item. This should be used just as you go for the first hit on an enemy or in team fights, try to time it so you can use it to sweep the remaining enemies before it runs out.

Highlander To wrap up his abilities, an absolutely ridiculous ultimate. More attack and movement speed to shred enemies to pieces and never be escaped from. Unable to be slowed. All cooldowns refreshed upon a kill. It really is just an all round crazy thing to have. The main problem I see people have with this ultimate is timing, it's fairly situational and not always just to use before you attack someone. If you can kill an enemy without it and you're low on mana, don't use it so you still have access to Alpha strike in case they escape or meditate if you get in a bad situation. Also when fighting champions who are fast / have flash or some other escape ability, save highlander until you are certain the kill is secured otherwise it might fade off before you get the kill and you'll miss the cooldown refresh.
There is varied opinions about using highlander for escaping, I think that it definitely should be used - It has a relatively low cooldown and you're more productive alive without your ultimate than dead with it. Enemies have to have a really good gank planned or do insane damage to kill you when you have Highlander and Cleanse up as nothing can stop you but death.

I use a standard offensive 21/9/0 mastery set, Although I also think a direct 31/0/0 set is viable seeing as Yi is a carry / assassin and should be played as one. Everything directly benefits your damage output, except Vampirism which is for survivability and Arcane Knowledge which is for early game harassing and farming power with Alpha Strike. I usually stick with 21/9/0 though.

Ghost I really like this for the mobility, escaping and chasing, but mainly the no unit collision. Getting stuck on minions while playing a melee character is NOT fun.

Cleanse As a primarily auto attack champion and a prime disable target, you never ever want to be shut down by Exhaust, Slows or Stuns.

Flash Lots of people swear by this. Personally I don't really like it, I prefer the speed and anti-unit collision anyway.

Clarity You do get mana starved fairly easily, but this definitely isn't necessary. Just be conservative.

Clairvoyance Good for map awareness but better suited to a support character. It could be used as a mini-flash alpha strike through a wall onto minions, but it's pretty limited and not as reliable as a ward.
Exhaust Good for 1v1 battles or shutting down auto attack champions. There shouldn't be too much that can defeat you 1v1 and the slow shouldn't be necessary to catch enemies but can help with teammate ganks and first blood.

Heal Helpful in getting first blood or surviving ganks. Not necessary most of the time due to lifesteal.

Ignite Good for 1v1, first blood and against champions like Vladimir, Fiddlesticks, Mundo, etc. There shouldn't be too much that can escape you so it's not really necessary. If you don't have this and the enemy teams got a fed vlad, mundo, etc. Buy an item with an active health regen reduction.

Rally Very limited use, the range on this really needs to be buffed or something. You move around lots as Yi so you'll probably go out of range. Could be helpful for first blood, better suited to a tank or support if used at all.

Revive Can be amazing and funny in the right situation. Cool down is too long for any real use.

Smite Jungling.. that's it.

Teleport Good for pushing towers and having less downtime for more money and experience, also usually necessary for solo laning. Can be good for ganks, teleporting to wards, shrooms etc. behind enemies and for back dooring. Movement speed is too high with Yi to make it worth it in most cases in my opinion.

This is very important to your success. As soon as you get Wriggle's Lantern, the buffs are both easy to take.

As you might know, Yi lacks any form of CC so enemies have a good chance of escaping you when your damage is still low. I can't really think of anyone who needs red buff more than Yi, you should ALWAYS have red buff especially at lower levels. Often times its not even worth attempting to kill an enemy champion without it.

Look at your team setup and see if someone else can benefit more from blue buff (Once your jungler has stopped). If there isn't anyone who specifically needs it OR you see an untaken enemy blue that you can steal, you should definitely grab it, the lower cool down on Alpha Strike is really great for harassing and farming minions.

I always pick up these items in all situations. These give you a free ward every 3 minutes, some lifesteal, good attack speed in combination with highlander, high critical chance to go well with runes and Infinity Edge passive. In the rare cases a game goes long enough or I've just been fed so much, I replace Wriggle's Lantern for another Bloodthirster and boots for another Phantom Dancer, Black Cleaver or Trinity Force.

During a game, I always start out with my boots and first 2 core items and my fourth item is usually where I start situationally picking items UNLESS the enemy team demands different items earlier.


Boots are completely dependent on the enemy teams setup, Berserker's Greaves are my most commonly used. If the enemy team is caster heavy or has too much CC for cleanse alone I'll take the Mercury's Treads.

The Bloodthirster I consider this a core item except in very rare cases where the enemy teams setup demands other items to be used. It goes well with the build, it gives the best AD from any item (Except a Sword of the Occult with >19 stacks..) and great lifesteal when fully stacked.

Banshee's Veil This is an all round item. If the enemy team has lots of casters, CC's or champs who really hurt with a certain ability and meditate / cleanse can't cover it all, this is definitely a great item. The passive increases are good for dealing with how squishy Yi is and his low mana pool.

Maw of Malmortius As an AD carry this is almost always better than banshees veil. If an enemy caster has spammable or aoe abilities, the spell shield from banshees won't do as much as you hoped for. Combined with your lifesteal, this can really save your life. The extra attack damage is a bonus as well.

The Black Cleaver Good against teams with Low - Middle amounts of armor. Since you already have runes giving you Armor penetration, this is almost always better than Last Whisper.

Frozen Mallet If for some reason or other you can't get your hands on red buff, you definitely need this. This item is great as it slows and also deals with how squishy Yi is. Little attack damage is a nice bonus as well.


Madred's Bloozrazor Standard counter against a team with lots of high health champions, though not recommended unless we're talking ridiculously high health. This is also viable against enemies with high armor and a thornmail, as you can shred 4% health per hit without taking extra damage from thornmail for it.


Force of Nature This very rarely happens, but if the enemy team are ALL taking thornmail and it is ruining your game it is actually viable. The magic resist counteracts thornmail since it returns magic damage to you, the health regen is a bonus. Decent as a counter to AP champs, but Maw of Malmortius or Banshee's Veil are better for that.


Guardian Angel If you're being heavily targeted in team fights and can't manage to stay alive, this can be great. After you die and enemies shift their attention to your teammates (who hopefully haven't ran off and left you for dead) you can pop back up and lifesteal your way back into the fight.


Thornmail If the enemy team is very AD auto attack heavy this can make you unbeatable 1v1 and turn you into a bit of an offtank.


Warmog's Armor This can turn Yi into an offtank. I prefer playing him as a straight DPS but this can make you fairly hard to kill with your lifesteal.


Randuin's Omen This counters how squishy Yi is, gives him a chance on being hit slow and an active aoe slow. Probably better than Frozen Mallet if the enemy team has bloodrazors.

Quicksilver Sash This item is like the superman version of cleanse. Removes EVERY debuff from you. It is the only way you can break Malzahar / Warwicks ultimates.

I've tried it out a few times and got some good scores with it - its pretty fun. But its definitely not viable unless you're skilled and have good awareness. You aren't going to get anywhere with it if you don't play like an assassin character eg. Evelynn, you lack the survivability to do more than gank really. Yi's Alpha Strike is his ONLY magic damage ability so you are completely shut down by banshees veil or magic resist. It makes for some fairly good meditate tanking, but that isn't really your role as a carry.
There is the possibility of starting out a game with a Doran's Ring, as this could boost your early game harassing and survival, then afterwards moving into an AD dps build. Although I don't really see the need for this unless you are solo laning.

I haven't played this much so I can't say much. I really don't think jungling is good to do unless you're doing a pre made team because it can handicap your team heavily if you make someone unskilled / unwilling solo lane. If you do have a skilled solo laner though, it could work out well.
Also, I incorporate jungling as part of my play anyway. As soon as I get my Wriggle's Lantern, if I get the chance I will slip out of my lane to kill a neutral mob, you can kill the buff minions aswell. Alpha Strike really makes it easy to do as well due to its chance for extra damage to minions.
Overall i really think smite is just a waste of a summoner spell because they are so detrimental to your success and you can jungle easily without it anyway so whats the point?

My first guide on Mobafire, please read, comment and vote (preferably in that order ;D). Just felt like writing this up for my first guide since it was fairly easy.. It kind of annoys me when I see people doing absolutely stupid things as Yi aswell :\ Hopefully this can be of some help to both beginners and skilled players, and also I hope it brings something new to the table for Yi guides - I haven't actually read other Yi guides so hopefully I'm not just regurgitating the same stuff the whole time.

Edits: - Changed masteries due to update
- Changed Stark's Fervor to Wriggle's Lantern due to its recent horrible death for all AD carries... Damn you Riot, why would you kill it like that Q_Q. Wriggle's is a good substitute and more team oriented though so it's not too much of a loss.
- Updated 4th October 2012 - Added some new item builds /edited out of date info, added more

Now go and rip enemies to shreds n_n