Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This is an attack speed build for Kass, I found it very effective. I'm not saying the AP build is bad, this just works for me.
Early game: Play passive, use your NULL SPHERE to get last hit on minions to collect gold. The moment you get 700g return, buy Philosper's Stone, and teleport back to your lane.
After you get enough for your Berzerker's Greaves go buy and teleport back to your lane. At this time you can harrass, make sure your FORCE PULSE is charged up ( use NETHER BLADE often to charge your FORCE PULSE)
NETHER BLADE > RIFTWALK > NULL PHERE > FORCE PULSE
( Remember use your cleanse and riftwalk to keep you safe )
Mid-Game: By now you should have your Zeal or even your Phantom Dancer, at this time you can almost gank at will. Use your teleport skill to jump to a lane and surprise your enemy.
Late-Game: You should have Wits End at this time, make use of its mana drain passive on low mana Champions, because you should be hitting really fast by this time. If you get in trouble cast Cleanse if stunned and RIFTWALK yourself to safety, Kassadin can escape almost any conflict if needed.
THis is my first build guide, please leave consturctive critisism and comments to help me in any way. Thanks