This build focus's mostly on Ability power, the reason is because Kassadin is very strong with his abilities, this build also focuses on getting cheaper items in the beginning to get a head start with the items to build up on in the future game. The 3 main starting items are movement, life steal, mana and ability.

The items are focused on ability, life steal, health, and mana, if you get the final item, (scepter) then you will be slowing down your target as well as damage them.