Sooo... After loong play with Kassadin i decided to make my own build. Why? Old builds can be good, but they are old. Just that's why.

Runes. What can I say about them. Kassadin need AP. Many of them. So there is magic penetration and many AP.

So it's classic start. Sapphire and 2 hp pots. After first comeback You should buy catalyst and maybe normal boots. Next You buy Majai's and Sorcerer's. Banshees Veil is just like another cleanse, so it's very usefull. Will of the Ancients let's You stay more on the battlefield and gives nice AP. Rabadon's Deathcap is just awesome, everyone knows. And Zhonya's Hourglass. This item is just soooo great at trolling ;). You Riftwalk into almost-teamfight-stance, use combo and Zhonya Yourself. So annoying. After that comes your team and real fight is starting (when enemy have less hp already).

After archie's opinion I decided to give that Chapt. You can always change Banshee's Veil for Rod of Ages. Do what You like. Hourglass can be swapped with Morello's Eviltome, or Lich Bane (I think Morello's Eviltome is better because of CD reduction). But I dont recommend to swap Will of the Ancients for anything. After taking dmg which makes you go town you can go jungle and fight longer.

YOU MUST GO MID. Thanks to that you fight 1v1, and there is your main power. Combos which You do are about how many stack at force pulse You have. 4? Make R-Q-E Combo. More? Use R-E-Q. In 1v1 always try to riftwalk as far as You can. Thanks to that Youre able to attack with W couple of times. When there are more enemy champs against You, try to dont go first. If It's not going to be a teamfight try to attack low HP targets being as far as you can use E and Q at them.

It's classic too, but i mussed change early. At level 3 you need some mana after harrasing with q, and after patch it gives much mana more, so it's worth ability point.