Remember the good old days? Back in Season 3, when Master Yi's were free to build as many Deathcaps as they wanted to, and still be able to swat down enemies with a single button press? I don't, but if you do, then congratulations.

Nonetheless, as of patch 5.22 Master Yi's are free to build Deathcap if they feel like it, given that they first grab a few lesser items. Well, not much lesser, considering they form the core of this build. Said items are your trusty old Sated Devourer and the reworked Guinsoo's Rageblade. Back during Season 5, your core would typically consist of Sated Devourer and Blade of the Ruined King, but recent nerfs to Blade of the Ruined King have reduced its cost effectiveness and overall power. While it has retained its full damage, attack speed, and lifesteal, it now deals only 6% of current health on hit as physical damage, as opposed to 8%. Additionally, it costs 200 more gold, a very significant amount when playing as a gold-starved jungler.

Guinsoo's Rageblade, however, has changed for the better. Its overall gold cost has dropped 100g, now only costing 2500 gold. Its on-hit passive has recieved a direct buff, now providing double the attack speed (8%), 4 AP, and 3 AD (infinitely more than before,) per stack! The icing on the cake, however, is that melee champions now recieve two stacks per attack with the new Rageblade, and when 8 stacks of Rageblade's passive are reached, it gains another on-hit effect, aptly titled Guinsoo's Rage. Basic attacks deal additional on-hit magic damage equal to 20+15% of your bonus AD and 7.5% of your total AP to both your target and enemy targets nearby it.

While one exceptionally strong item combined with another is enough to push any champion over the edge, AP Master Yi has two more powerful components to his build. The somewhat reworked Hextech Gunblade, and the slightly-buffed Nashor's Tooth.

Since Nashor's Tooth requires somewhat more AP than that provided by Guinsoo's alone to be useful, Hextech Gunblade comes next in the build.

Gunblade's new passive, changed from having seperate lifesteal and spellvamp components to a blanket, 'Gain 15% of all damage dealt in health', is great for Master Yi, as his E, Wuju Style, deals true damage, something not affected by lifesteal or spellvamp. This new passive, however, does proc off of true damage, allowing for a reliable source of sustain against tankier foes. Gunblade's active also fills the role of the abandoned Blade of the Ruin King's active, applying a slow and damage at range, as well as a slight heal from the passive.

Finally, you'll want to build a Nashor's Tooth. The extra attack speed is very useful for pure DPS, allowing you to apply Devourer, Guinsoo's, and Wuju Style's damage more rapidly, while the extra AP increases the damage from Guinsoo's on-hit effect, and increases the healing amount from Master Yi's W-Meditate.

The capstone item for this build is typically Rabadon's Deathcap, though it could feasibly be exchanged for an Abyssal Scepter, Void Staff, or any situational item such as a Guardian Angel.

Your boot choice should typically be Berserker's Greaves or Sorcerer's Shoes, depending on whether the enemy tanks are stacking health, like Sion, Dr. Mundo, or Tahm Kench, or resistances, like Malphite and Rammus. Your enchantment, now that everyone gets free homeguards, should be Furor, Alacrity, or Distortion. I personally recommend Teleport/Smite Yi with Distortion.

Mastery-wise, a typical ADC build adjusted for the jungle (This is actually the ideal Mastery Page for Jungle Kindred as well), such as the one above, works wonders. For your Rune Page, Armor Seals, Scaling MR or AP/Scaling AP Glyphs, plus AD or Hybrid Penetration Reds is ideal, topped off by Attack Speed Quints.

Generally, your playstyle as an AP Master Yi will be similar to AD, with a few key differences - for one, you are much more sustainable in extended combat. Second, your damage is much harder to itemize against, dealing almost equal amounts of physical and magical, as well as true damage from your E. AP Yi is also much more forgiving of mistakes thanks to the bonus healing W grants with your AP items. The most major difference is that with this build, your Q does less damage than building AD, and you will not be building for crits. While your damage will be far more reliable, the lack of critical chance means that your damage spikes may suffer slightly, your Q (Which can Crit) in particular.

Granted, this build requires preestablished proficiency at playing Devourer Junglers and Master Yi in general, but once those requirements are met, you too can pick up Season 6's AP Rengar.