Master Yi is a melee DPS auto-attacker with high attack damage, attack speed, and mobility. He excels in 1v1 fights and is known for backdooring, jungling, and soloing Baron on Summoner's Rift. All for only 450 IP.

He often is criticized for lacking crowd-control spells (stun, slow, etc.), having an out-of-place Meditate, and general inability to contribute in teamfights. Most players build him squishy AD/AS or AP.

However, in Dominion champions dealing high sustained DPS are the champions to play. In a map requiring mobility and high damage output, as well as encouraging smaller skirmishes, Master Yi is a great pick. In Dominion, his role mostly stays the same: a killing machine.

I hope you will enjoy this guide, written by me, Cottonycloud, a 1275 (1401 pre-reset) elo NA player. Most times I will leave up building to the reader because of different playstyles. Please don't charge in 1v5 and then say that my guide sucks.

Ghost - Use this instead of Highlander. For utility.

Exhaust - Absolutely needed to take care of other AD carries. And slow! (Less running, more killing)

Flash- Like Ghost, but you can't get around the map with it.

Less Viable

Garrison - Exhaust is more useful.

Promote - As a pusher it's okay, but exhaust is more helpful.

Ignite - You are Master Yi, and Ghost and Exhaust are better.

Cleanse - Quicksilver Sash deals with suppress, but this has a reduced CC duration effect. 150 second cooldown also! It got buffed a little, so if you include this, switch out Quicksilver Sash for something else.

Heal - You have meditate and heal shrines. This lowers healing as well.

Surge - Maybe. It's more for supports than Yi though.

Just Don't

Runes include armor penetration, which scale well late-game, as well as some bulkiness to improve survival capabilities.

Feel free to switch out with any of these, for whatever reason.

Other Runes

Greater Quintessence of Health - Tanky!
Greater Quintessence of Movement Speed - For speed.

NO mana regen, reduced death timer, GP5, magic pen, or AP runes!

Double Strike - Every seventh strike Master Yi attacks twice. Getting attack speed early allows you to capitalize on this.

Alpha Strike - A gap-closer that renders Yi invulnerable for a short duration while giving the opponent time to respond. It has a chance of dealing 500 damage to minions, excellent for farming. Also, casting on a dead minion or champion will cause you to end up where you stood originally after.

Meditate - In general, lackluster. It allows for some sustainability, but is essentially useless if there is stuns or knock-ups (smaller fights = less disruptions). Resistances are gained while casting, up to 300. Use this or Quicksilver Sash when blinded, exhausted, or under threat of taking large amounts of damage (Karthus ultimate).

Wuju Style - This is how he hits like a truck. Removes passive effect afterward so be careful when you use it (sometimes).

Highlander - Think of Youmuu's Ghostblade, but better. This refreshes cooldowns upon kill and half upon assist. However, despite the movement speed buff, you should never use it to run up to an enemy. Use Ghost and Alpha Strike instead.

Skilling Order

Always start with 2 Wuju Style and 1 Alpha Strike for maximum damage output. Max out Wuju Style first, and at the same time you can switch off between Meditate and Alpha Strike for a balance between easy farming and sustainability.

Usual Scenario

Ghost, Alpha Strike, Exhaust, pop E and R, right-click. QSS if any CC. You Have Slain An Enemy.

Overview

Going glass-cannon on Yi is not recommended, though you may get by in lower-skilled games. The problem with getting only damage items is that you will almost always die before dealing any significant amount of damage. Therefore I run a build centered around bulkiness while at the same time dishing out some damage.

Starting out with HP is a must: in the first fight at top you are almost always exhausted and focused. The HP allows you to tank damage for your ranged teammates.

Long Sword allows you to quickly upgrade to a Phage which provides a nice slow, while Dagger gives you the most damage output if you simply stand and auto-attack (this rarely happens, however).

Prospector's Blade slows down your build; however, if you plan on getting Lifesteal, you may want to put this into consideration.

But do not, DO NOT I SAY, get Vampiric Scepter! You heal about 15 health every attack, but in the first fight, you are either full health or too low to expose yourself by attacking! If you got bottom for some reason, it is not so questionable.

Whatever you do, get Tier 1 boots and upgrade according to the situation.
Upgrade Zeal, boots (Mercury, Ninja Tabi, Berserkers), and you can buy Avarice Blade if you want.

Akali's frequently played at the moment, so consider buying a Recurve Bow in preparation for Lightbringer.
Upgrade Phantom Dancer for mobility (leave it as Zeal if there's smething else of more importance), buy Phage for HP and CC (upgrade later to whatever you like), and a Quicksilver Sash. Get Chainmail and prepare for Infinity Edge.
Get Lightbringer if you have to. You should be around level 10.
Upgrade to Atma's, upgrade Phage to whatever you like (Trinity/Entropy), and finish.
You can trade in Atma's for a more aggressive item such as Youmuu's or another Phantom Dancer. Replace QSS with Odin's if they have barely any CC. You can buy Thornmail, Warmogs, Guardian Angel or an offensive item instead.

Lightbringer/Oracle's against Stealthed.

SotD for Jax.

Maybe Executioner's Calling

OTHER ITEMS

In general, NO HEALING REGEN, MANA REGEN, AP, OR MANA. Please.

Youmuu's Ghostblade - increases damage output more, but Phantom Dancer has movement speed for walking around the map.

Sanguine Blade - Healing regeneration is reduced...but if you insist. Just don't stack them though.

Kitae's Bloodrazor - Youmuu's improves your damage output more.

Ionic Spark - Meh. At least you're still in the attack speed category.

Odyn's Veil - only get if they have no CC and they have more magic damage. The active's damage is too weak.

Stark's Fervor - The regen is useless because this is Dominion, and regeneration is reduced anyway. Attack speed and Armor pen is okay, but there's Youmuu's if you want that.

Hextech Gunblade/Guinsoo's Rageblade - NO!

Tiamat - Get anything above this, as long as you don't get this. Even weaker in Dominion.

Boots of Mobility - Better with Rammus. You're fast enough!
Boots of Swiftness - If you want mobility, get above boots. You hardly get hit, so that will help you more.
Boots of Lucidity - NO.
Sorcerer's Boots - um what?

Thus is my guide. Hope you liked it. However, do not scream "NOOB BUILD" or "YI SUCKS!" if you run in 1v5.

10/1/11 Added pretty pictures to summoner spell section. Rearranged sections.
10/2/11 Replaced Phantom Dancer with Zeal in cheat-sheet. Replaced Perseverance with Good Hands in masteries. Tweaked masteries section.
10/22/11 Removed wordiness in some sections.
10/23/11 Cleaned up skills. Comment no longer required to vote. Downvote to your heart's content. =)
11/6/11 Removed icky color from items. On process of fixing it up.
11/10/11 First half of the items section improved. Double Daggers and Avarice Blade now removed from starting items section. Really, what was I thinking?!
11/23/11 Revamped masteries. Cleanse is a pain too.

Items section, videos, screenshots, wordiness, and guide aesthetics are next in line.