Hello guys this is Dzoni and this is short guide.First to discuss about Kassadin.It is a good late game champ(in my opinion one of the best).First you must be sure to provide a good early and mid game to be an op in late game.First he have short cd ulty.Thats why you dont need flash.He also have a lot of cc(silence and slow).He is an anti-mage champ cause of the silnce and passive.He is mana depend too but he can gain mana from the 2nd ability.This is why you need Tear of The Goddess.Then you rush for a full boots and Rabadon Deathcap.Boots provide you more mobility and rabadon high dmg.As Tear is stacking mana you can buy some hp.You can get that from Rylai's Crystal Scepter.Now you dont need to relay only on your ulty.If game goes on you should buy some magic penetration.You archive that with Void Stuff and Abyssal Scepter.
Thats it for now.I will see you all next time!