First off, I accidently down voted...sorry :/ Meant to +1 - I need to pay more attention.

It's a nice build, and seems like it would make for a really great Kassadin, but there are a few things I disagree with. Especially when you say Void Sphere is too little damage for too much cost. Void Sphere is how I get a good 5+ kills in the first 10-20 minutes...and Force Pulse requires you to get a bit too close for comfort, in my opinion. But, if that's how you like to play, I'm not trying to stop you. Anyway, it's a nice build, wish I could +1 it...but...yeah. Sorry about that!

Who is this adressed to? If to me; I didn't vote...

I find that even though Kassadin is a great champ, he is a lil squishy. I've got a build, and Ive taken RoA. It helps with the low mana pool and extra life and AP isnt bad either.

I like the build, and I like the Defense aspect of play. Makes you a lil more tanky. +1

itll be less MP. i assure you dont need rod. and 27 is a good bonus from glyphs

its a very nice build but masteries and glyphs are wrong >_>

Change defensive masteries to utility so you can spam spells even more.

Make seals to be mana regeneration per level and change the third quintessence to be flat ability power.

Anyways for good explanations and good build just change haunting gale to rod of ages it will be better.

+1

ok here is a deal i will vote yes and you and your friend who voted no on my vote yes.

okey. that was quite bad from you to do -1. just for you i v done some changes. and it work just fine. even better then befor. ths man

You don't have to do anything. I'm just recommending you take another look at other options. There are a few lovely choices availible :)

hmm. not bad. but dont you think full AP runes are better?

This build is very very very cool

This could work. It will however need some major modifications to handle big challenges..
I recommend that you investigate other choices. Especially in runes and masteries.

good job, gozip. Thanks for guide