Keeper of the ancient art of Wuju, Master Yi is a mystical warrior from the isle of Ionia. He descended from one of the few tribes dedicated to the preservation of Wuju, a martial art founded with the principles of absolute spiritual awareness of one's self and one's enemy. When the armies of Noxus invaded Ionia, Master Yi joined in the Ionian defense to fight the craven enemy, bringing his village honor through his unparalleled mastery of the blade. The ensuing battles ravaged the land, but no conflict inflicted as much horror as the day the armies of Noxus closed in on Yi's village. Left undefended, the village became the unfortunate test subject of the latest invention by an up-and-coming chemist, now known as Singed. The remains of the village that Master Yi returned to were so horrific that it remains a festering scar on Ionian history. To this day, no Ionian will ever publicly speak of what occurred.

After the Noxian invasion was contained, Master Yi fell into a deep isolation. For years, he trained morning to night, speaking to no one and refusing offers of consolation by fellow Ionians. The only thing stopping him from madly charging into Noxus battle lines headfirst was his pledge to keep the Wuju style alive. Even though he seethed with impatience, his rage became a tool for sharpening his practice of Wuju, developing stronger and deadlier skills for his eventual vengeance. The only thing that roused him was news of the League's formation, and Noxus' subsequent enrollment in the League. Master Yi now brings his mastery of the blade to the League of Legends with unflinching purpose: to avenge his kinfolk and end the predations of the Noxus once and for all.

Deathfire grasp has been changed.. Much more dmg output now :)

Hiho..
Before reading this guide i have to complain the PRO's and CON's of AP Solo Top Master Yi.. I cant understand why some thinks AP Yi is actually a bad option to other AP Carrys.. So here it goes, have fun reading my Guide:)

Pro's:
-Great Lane sustain because of his Meditate.
-Good harrassament because of his Alpha Strike .
-Awesome Burst Dmg. in combination of Alpha Strike and Deathfire Grasp.

Con's:
-CC Counters him hard.
-Just 2 real attacking Skills.

I Prefer taking Flash and Ignite Flash for your escape and Ignite for your decent extra dmg., you rly will need it

I Prefer taking 21/9/0 because of the dmg and you have to suffer against bruiser Top enemys.
http://imageshack.us/photo/my-images/16/neuebitmap2h.png

The runes i take are not typical for an AP Carry, but i play him a bit different because i think as a solo Top champ. you need these sustain Runes.

-9x Greater Mark of Magic Penetration You need them to penetrate the m. resistance of your mostly bruiser solo Top Enemys.
-9x Greater Seal of Armor Need them for Lane sustain.
-9x Greater Glyph of Magic Resist i dont know why, but they dont Exist in Mobafire database. W/E you need them for the Lane sustain.
-3x Greater Quintessence of Ability Power For the decent extra dmg.

Q - Alpha Strike - You will strike the enemy Target and 3 other nearby Enemies before returning to the enemy you clicked. Its a 1:1 AP ratio.

Its your main skill as AP Yi, Awesome burst, Aweseome AP ratio, Awesome harrass and farm

W - Meditate channel for 5 seconds, healing and gaining armor and mres. 1:1.65 AP ratio

Great defensive and survivability skill. Allows you to lane for a really long time as well as giving you the sense that you have double the amount of HP that you really do.

E - Wuju Style passively gains attack damage, actively doubles the passive amount. On cooldown the passive is negated.

Gives nice attack dmg but you quiet dont need it as AP Yi so set a point at level 4 and max it with level 18.

R - Highlander increases movement and attack speed, ignores all slows, upon killing an enemy champ you refresh all cooldowns, upon getting an assist, you reduce your cooldowns in half.

This skill is needed for escape or for starting a fight.

I Normaly start with Doran's Ring another option to Doran's Ring are Boots and Health Potion but i prefer Doran's Ring you can easily Heal up with your Meditate
At the first Backporting to Base rush for another Doran's Ring and as fast as you can go for Boots
Then start building Deathfire Grasp i prefer to start with Kage's Lucky Pick then rush for Deathfire Grasp (Don't forget using the active of Deathfire Grasp)
As next you have to build your shoes, take Sorcerer's Shoes or Ionian Boots of Lucidity they are both good Sorcerer's Shoes for more dmg and Ionian Boots of Lucidity if you want to use your skills more often.
Next item is your major dmg. Item Rabadon's Deathcap, important is to get first Needlessly Large Rod, then you will deal awesome burst dmg.
After finishing Rabadon's Deathcap start with building Void Staff when you finished this item you will totally deal mega burst dmg. to everyone in enemy Team.
Now you finished your major dmg. items, next point is to Build 2 suffer items for Sustain:
Zhonya's Hourglass and Abyssal Mask Are a great choice.

Optional Items:

Rylai's Crystal Scepter - If you want more Health and a slow with your Alpha Strike its a good optional item.

Lich Bane - If you want a bit more m. res, M. atk. and the powerfull Active/passive of doing a hit after Alpha Strike.

Will of the Ancients - You heal Quiet alot with your Meditate and Alpha Strike.

Banshee's Veil - If enemy Team have much CC This item would be pretty usefull.

Early-Game (15-20 min.)

You start with Doran's Ring head to your lane and try to not harrass so much with your Alpha Strike because you will be ganked fast if you do so. Stay in lane as long as you could, go back when you can afford 1 more Doran's Ring and Boots. You have to be carefull and always place a ward in the river. When early game is finished you normally finished your Deathfire Grasp and Sorcerer's Shoes.

Mid-Game (20 min. till 30-35 min.)

In Mid-Game you are going for killing Sprees, ganking on other lanes and pushing Turrets. Try to get as often as you can a Blue buff, you really will need it.
You normally finished your Rabadon's Deathcap and Void Staff at the end of Mid-Game and beginning of Endgame.

End-Game (35 min. - till end of the game)

At this Point you really Have to carry the Game because of your farm and kills. If the game is not over Yet build Zhonya's Hourglass and Abyssal Mask. Heading to the end of the Game Master Yi is not that Usefull, you have to Win earlier.

Its my first Guide, so pls vote and place your comment below.

Thanks for reading my guide. :)