This guide is a build on kassadin that works! Using this build i carry the team with kass every game almost. Usually i mid with kass so that is what i suggest you play. For runes just use mana runes and ap ruins [Ability Power] along with some magic penetration. Masteries are 21 [Offense] 0 [Defense] 9 [Utility]. I use theses masteries because after exploring different builds with Kassadin this one is best for the build and runes i use in this guide. Skill sequence is very important when playing Kassadin, In early game you should try and just stay back and farm and maybe harass a little with your q. But once you hit level 6 is when you can really start harassing your opponents, the sequence is Riftwalk [R] then Null Sphere [Q] for harassing then once you reach 4 on abilitys used for your E then the sequence is [R] [Q] [E]. Then go back to farming using your [W] to regain mana. For summoner spells i use flash and ignite, i know it may seem silly to use flash because you have riftwalk but believe me when your rift walk is on cooldown and you really need to escape, you will have your flash. Kassadin is the master of jukes and get aways this way. Then i use ignite because it works very well for when you have your enemy hiding under turret with low hp [Health Power]. You can riftwalk to enemy do your combo then ignite and flash out safely and get the kill.

Thanks for looking at my build and please vote this up!!!