My version of Kassadin rework (numbers not included-ish)

Basically, my rework will focus on Kassadin juggling the use of his connection to the void. Using spells grants him stacks which he can then use. This is also a more thematic way to gate Kassadin rather than having mana costs in the thousands. Feedback appreciated.

Kassadin the Void Walker

Passive void stone: Kassadin takes 15% reduced damage from spell and restores mana equal to the amount of damage reduced. His spells also unleash void energy that can be used for other spells.

Q: Null Sphere: (single target nuke) Kassadin fires a sphere of void energy at a target. The release of energy grants Kassadin more move speed. This can stack up to 3 times. The duration lasts 5 seconds. Each new stack will refresh the duration. The duration is refreshed if a spell is used and Kassadin already has 3 stacks. If Kassadin has at least one stack, his other abilities can add stacks. Only this spell can place the initial stack.

W: Nether Blade: Active: Kassadin's next X auto attack(s) will deal bonus magic damage. Passive: When Kassadin casts a spell, including this spell, he gains a "Blade" stack. Kassadin can hold up to 6 "Blade" Stacks. When this spell is activated, it will consume all available stacks. Every 2 stacks consumed will grant an additional empowered auto attack. If this ability is activated and no stacks are available to be consumed, Kassadin will instead gain a minimal amount of mana for one auto attack. Single consumed stacks also have this restriction.

E: Force Pulse: Passive: Kassadin draws energy from spells cast in his vicinity, gaining a charge whenever a spell is cast near him (including his own spells). Upon reaching 6 charges, Kassadin gains the ability to cast Force Pulse. Active: Kassadin can emit a pulse of void energy, dealing magic damage in a 80 degree cone in front of him.

R: Rift Walk: Active: Kassadin teleports to a nearby location, dealing magic damage to enemy units within 150 range upon arrival. Passive: When Kassadin casts a spell, not including this spell, he gains a "Walk" stack. Kassadin can hold up to 6 "Walk" Stacks. When this spell is activated, it will consume 2 stacks. This ability cannot be activated unless at least 2 stacks can be consumed.