http://blogfiles.naver.net/20150225_277/ars2886_1424837224903jOowe_JPEG/q1.jpg Kassadin is just human and he stole the infamous 'Nether Blade of Horok'. also He have a armor.
Why he use viod energy? Maybe 'Q' skill(Null Sphere) His story isn't included. How he can use viod energy?
In-game abilities are not necessarily canon and Kass is a pretty old champ with a lot of previous retcons to his character.
But I'll try my best to speculate on the topic (this is my 5 cents, do not take this as canon)
Kassadin uses armour and other armaments and gear to withstand the void's corruption. Note that the corruption does not enhance in anyway. The corruption would not give Kassadin crazy abilities to shoot plasma.
But look at it this way, the stuff Kass wears, where does the energy it absorbs go? Could it be possible the energy Kass uses is him simply expelling in the form of purplish glowing energy?
If I had to VGU the champion I would make the Nether Blade responsible for his Void powers
"Nether" means lower in position and where is the Void? Below.
Also cool to think about an Ascended that mastered the Void and created a weapon to manipulate it.
Probably Kassa's geat absorbs the Void energ6 when he kills Voidborns.
Kassadin used a lot of different unknown means to get the power he currently has so we don't know all the powers he could actually have in lore. That being said Kass model and abilities are really old so I would wait for a proper VU before we bring his abilities into lore discussions.
His story now says that they are all relics and tech that he got by calling in favours in order to achieve his goal of destroying the void. Personally i feel if they were going with that they should be more imaginative or at least give some recognition to wtf these things are. Ex. a void blade doesn't make sense because the first instance of the void being quote um quote weaponized is when a rift was opened resulting in the fall of icathia, until kai'sa (supposedly kassadins daughter) stabbed a voidling and it's ooze became a symbiotic suit that grew with every voidborn she killed there is no record of weapons that utilize the void, only those who directly serve the void like malzahar and the voidborn. His passive is called void stone so he somehow got ahold of an object from the void that there is no record of and we have know idea how it work's and uses that to teleport and stuff- looking at his original concepts he seems like he might have more runic/crystal(hextech) focuses so he needs an update to what these things are, what they can do, and where do they come from,
