Kassadin Build Guide by BBerger

Introduction

Rifts in the Forest, A Twisted Treeline Kassadin Build

Greetings, I am BBerger. I made this build after I have played a streak of many dozen matches as Kassadin on Twisted Treeline, the 3v3 map for League of Legends.
With the help of some more skilled and experienced players, I've gained experience myself in the strong pick of Kassadin. Twisted Treeline all comes down to a few traits: Survival, Mobility and Early Game Strength.
Kassadin is very strong in both Survival and Mobility; he has Null Sphere as a nuke and a silence, Force Pulse: a powerful slow and nuke as well, Void Stone, and his ultimate Riftwalk allows him to blink over the many walls of Twisted Treeline to avoid and survive confrontation. He lacks early game strength, however, and this build tries to compensate that flaw.

Kassadin & Twisted Treeline

Kassadin is a viable, strong pick in Twisted Treeline. As described in the introduction, he has powerful skills that make him somewhat more viable in Twisted Treeline than in Summoners Rift.
In Summoners Rift he has to fight versus five, he's squishier and may have a harder time pinning down a target. In Twisted Treeline you only have three targets to do damage to you, your Null Sphere silences 1/3th of their spell arsenal, your Force Pulse can slow and damage their entire time. Simply put, Kassadin has an easier time in Twisted Treeline

A couple of hints if you're used to 5v5:
= You are a strong solo (top) laner with a ranged silencing nuke
= Don't try to gank early, you're a burden for ganks till level 6
= Twisted Treeline matches are short and easily snowball from an early 4 kills to a victory.
= Kassadin's biggest flaw is dependency on his ultimate and lower than average mana pool.
= It's better to space the time in your Riftwalks, that way it's not so mana intensive
= If you Riftwalk into solid material, you will 'bump' to the nearest open space; this can greatly increase your jump space. Warning: Kassadin/Flash Experts Only!
= Be mobile and gank whenever there's the opportunity and high chance of succeeding.

Runes, Summoner Spells

Runes

Greater Mark of Magic Penetration
Magic penetration is rare and strong; either you're forcing them to go Magic defense and still do good damage, or they don't and you slice through them. You won't have Sorcerer's Shoes in this mode, so take the runes.
Greater Seal of Armor
"Armor? Pff!". Yes, armor. You have very low armor for an Assassin, you start with 17 armor. With Doran's Shield and these runes, you're all set for the largest portion of the game. If you think you need more armor, check out the Optional Items down below.
Greater Glyph of Scaling Mana Regeneration
The blue runes is what I have the most doubt about; you already have Clarity for mana regen, but it will be on cooldown a lot as well. In the end, I think these mana runes will save you more by giving you more Riftwalks.
Greater Quintessence of Health
Health. You can't honestly have anything to say to that. It's far too strong in Twisted Treeline to pass on 80 health.

Summoner Spells

Ignite
I'm not an Ignite fan personally. Really, I'm not. But you already have the mobility of Flash and Ghost combined in Riftwalk. Ignite does a lot of damage and can help you burn through a squishy caster or put pressure on a more beefier target.

Clarity
You chuck down mana like a miner chucks down beer in the weekend. Even with great mana management or rushing 5 points into Nether Blade, you're going to starve for mana. You will not regret investing in Clarity.

Exhaust
I know people are going to try and suggest this. The answer is no. It's worthless. Your Null Sphere silences, and coupled with Riftwalk reduces their damage output to you to zero. You also already have a slow in Force Pulse, and even if you put a mastery point in it, you will still have more penetration with Haunting Guise and Nether Blade.

Flash
You are already godlike mobile. Null Sphere silences them, so if you cast it before using a Riftwalk to escape, they cannot follow you with their own Flash, if that's what you're afraid of. Not to mention your Riftwalks are too spastic to react with a flash.

Items

Armour, Health Regeneration and Health. Trust me when I say that this is stronger than Doran's Ring, this gives you stats you really need early game.
Health, Ability Power and Magic Penetration. In Summoners Rift, there are better items. But not in Twisted Treeline. This will give you the damage and survival you need to gank.
Pure Ability Power. Only get this if you have kills. Twisted Treeline is a gamemode that snowballs very quickly; if you're doing very good early game, get this to guarantee that you will profit from early kills.
Movement Speed, Tenacity and Magic Resist. You can't afford to spend your money on anything else but Tenacity. Sorcerer's Boots might increase your damage, but with Mercury's Treads you will be able to cast and escape easier.
Pure Ability Power. Always invest in Needlessly Large Rod first; there's a large 'pause' between Haunting Guise and Mercury's Treads where you still do a lot of damage and are able to survive a lot of battlesm to the point where you have to increase your damage to compete. 1600 gold is a lot of money in Twisted Treeline, so die little, farm and gank often when possible, and the sooner you get Needlessly Large Rod, the quicker you have the advantage over them.
Ability Power, Burst and Magic Resist. I've never really gone for a match for so long I got Lich Bane, but it should be the only item left after Rabadon's Deathcap, unless you want an Optional Item(see below).

Optional Items

Magic Resist and Magic Shield. Build this after you get your Needlessly Large Rod, and start with a Negatron Cloak. You can always build Rabadon's Deathcap after the cloak, and then build it into a Banshee's Veil; that way you will maximize both damage and survivability. Banshee's Veil is an item you should get if they're primary damage is magic or one particular ultimate to initiate with.
Invulnerability Shield, Armor and Ability Power. Replace Rabadon's Deathcap with the Zhonya's Hourglass if their physical damage is off the charts, and you really need to survive their carry potential.
Attack Speed, Mana Regen, CDR. Replace Lich Bane with Nashor's Tooth if your and their team has a lot of bruisers. They'll expect you to stay within the teamfights and they can't risk trying to let you kite. You'll substitute the burst magic damage with the extra sustained magic damage from Nether Blade and attack speed from Nashor's Tooth.

Summary

All in all, this build focuses on closing the gaps that make Kassadin not a top-pick in Twisted Treeline. In truth, he's one of, if not the strongest caster in Twisted Treeline, thanks to his beefiness, damage, crowd control and mobility.

And in truth, this build is just here because there is no Twisted Treeline build for Kassadin on Mobafire. I'll gladly add more section, answer questions and reply to comments to improve this build.