Mathematically Correct Kha'Zix (Updated Occasionally)

Mathematically Correct Kha'Zix (Updated Occasionally)

Chilling Smite
VS Squishy 
Only use this if you have Nimbus Cloak 
Challenging Smite
VS Bruiser 
Skill Order:
Taste Their Fear
Void Spike
Void Assault

UPDATED PATCH 13.10: Edge of Night is pretty good right now, 3rd or 4th after Ghostblade is viable

-Introducing: I'm a Diamond 4 Kha'Zix main who plays on Vietnamese server. I have played over 2300+ games of Kha'Zix since season 9, had 800k mastery on my main account and 200k mastery on alt, therefore I have decent knowledge about his strengths and weaknesses. I made this guide because many people are building Kha'Zix wrong and I'm here to lead you to the right build.
-About the build: Maximizing damage from Q (Taste Their Fear) while having enough sustain and tankyness to duel every single champion in the game. My goal is to turn Kha into a stat-checker by buying items with high-damage stats & also synergy well with him.
-There are currently 3 build which you can go: Eclipse/ Prowler's Claw/ Bruiser build with Divine Sunderer. In this guide, I will only be talking about Eclipse build, which IMO, is currently, and possibly the all time best mythic item for Kha'Zix.
-Why no Duskblade? Lack of damage compares to every other core mythic items. Don't get me wrong, it's still viable up to challenger level but in order for it to work, you really have to trust your bronze teammate. Moreover, that build requires some times to get used to and overall offers completely different playstyle (you have to play like a rat) if you want to get the max out of it.

Let's get straight into the build here: Full lethality & armor penetration to maximize Q damage. Omnivamp makes up for the lack of sustain.

-Eclipse is gonna be the first item, as it provides anything an assassin needs: damage, sustain, and movement speed. With its component being extremely efficient on Kha'Zix, it is no doubt the BEST mythic item for our beloved cockroach. Second place belongs to Prowler's Claw. It used to be the best item you can build on Kha'Zix due to its mythic passive plus 5 lethality for every legendary items you have. Which, statistically meaning, if you have full build, this single item can give you up to 46 lethality (??!?). But in patch 11.13, it got nerfed quite heavily, from the raw lethality it gives, to its active cooldown. Nowadays it's still very good, but there's not enough reason to take it over Eclipse. Some flashy tiktok video can be made with Prowler, but for the shake of your LP and your teammate, don't.

-Boots: Boots don't really matter. You can either take defensive boots with merc for hard CC teamcomp, ninja against heavy AD, or maybe for offense purpose, it's a matter of personal preference. You can opt for swiftness boot or no tier 2, saving gold for powerspike item if you're fed. CDR boots help you jump around more comfortably, while significantly reduce your spell cooldown by a bit.

-Next item, Ghostblade. Very standard here, nothing out of ordinary. Movement speed when out of combat? Seems good. Lots of lethality? We take those. The Collector is not our option. Very interesting passive but anything besides that it is just a waste of gold. Less lethality, bad gold efficiency, that's an instant pass.

-Next item is Essence Reaver. Kha's kit relies way too much on isolation, this item can somewhat fix this weakness. Don't worry about the sheen effect, it's actually really good on him. This item also makes clearing camp or taking down drake much faster. On top of that, it ensures you don't run out of mana while in combat. Essence Reaver is a very underrated item which Kha can comfortably abuse.
-Fifth item is Serylda's Grudge or a defensive item. You got more than enough lethality and heading toward mid-late game, therefore the only thing you need now is some armor penetration or defensive item. There used to be a time where you had the option to either build Serylda's Grudge or Lord Dominik Regards (LDR) but after the nerf to LDR, Serylda was proven to be the superior one. The perma slow is great and can single-handedly win you the fight.
-Last item is situational. It can be any items really. At this moment you don't really need more damage anymore so building defensive should be the main priority. Could be:
+ Guardian Angel: Good overall vs AD comp. + Death's Dance: Good overall vs AD comp. + Edge Of Night: Prevent CC or range abilities (Lux Q, Zoe E, Fizz R, anything has a lot of range that can one shot you from miles away). + Maw Of Malmortius: Good against AP comp. + Bloodthirster: More damage. Don't go nut with this though, not actually that good. + Randuin's Omen: Against 4 or 5 ADs.
-Skill Order: Q -> E -> W

IMPORTANT: DON'T MAX W SECOND, PUT 2 POINT ON W THEN MAX E AFTERWARD (E is much more important mid game due to its low cooldown when maxed)

  -Evolve Order: Q -> E -> W if their enemy team has 3 or more squishies, otherwise Q -> E -> R. R is good for extended teamfight while W is good at isolating and bursting down single target.