[Champion Concept] Rix'Khan, Lord of the Void

Hello there, fellow Summoners. I am Captain Wednesday, and I would like to present to you my champion concept, Rix'Khan, Lord of the Void. He was my first out of around 20 champions that I have created. This is my take on a true Hybrid champion. Please, feel free to comment. Also something to note, his name not a flip-flop of Kha'Zix. Rix is a Void word, and Khan means "king", which is why he is the Lord of the Void. Without further ado, here is Rix'Khan:

Rix'Khan, Lord of the Void Primary Class: Assassin
Attack Power - 8 / Defense Power - 2 / Ability Power - 6 / Difficulty - 7

Health: 435 (+81) / Health Regen: 6 (+0.65) / Mana: 270 (+35) / Mana Regen: 6.75 (+0.5) / Range: 125 (Melee) / Attack Damage: 50 (+3.25) / Attack Speed: 0.67 (+2.5%) / Armor: 16 (+3) / Magic Resistance: 30 (+1.25) / Movement Speed: 345

Lore: TBA
"I was worshiped in the Void. I shall be feared here!"

Passive - Void Empowerment
Whenever Rix'Khan damages an enemy unit with an ability, he gains a stack of Empowerment. Empowerment stacks grant 2% of his Attack Damage and Ability Power as bonus Attack Damage and Ability Power, respectively. Rix'Khan can have up to four stacks of Empowerment. These stacks decay each second once out of combat.

Q - Zero Energy Lance Cost: 50/55/60/65/70 mana / Cooldown: 12 seconds
Rix'Khan hurls his spear in a line, dealing 75/105/135/165/195 (100% of bonus AD) physical damage and rooting the first enemy unit for 1.25 seconds. If Rix'Khan is near the rooted target, he may recast Zero Energy Lance to lift the root from the unit. The unit then bleeds, dealing 10/20/30/40/50 (15% AP) magic damage over four seconds. Rix'Khan gains 20/25/30/35/40% movement speed for four seconds if he recasts Zero Energy Lance.

W - Dark Assault Cost: 60 mana / Cooldown: 26/25/24/23/22 seconds
Passive: Rix'Khan passively gains 2 AD & 6 AP / 4 AD & 12 AP / 6 AD & 18 AP / 8 AD & 24 AP / 10 AD & 30 AP . This passive is lost while Dark Assault is on cooldown.
Active: Rix'Khan jumps to target enemy unit, dealing 60/85/110/135/160 (50% total AD) physical damage. If the target has the Zero Energy Lance attached to them, Rix'Khan will deal 4/6/8/10/12% of their current health as magic damage.
Note: Dark Assualt's passive is lost after damaging a target.

E - Void Ray Cost: 70/75/80/85/90 mana / Cooldown: 16/15/14/13/12 seconds
Rix'Khan conjures a powerful void energy blast dealing 70/110/150/190/230 (65% Ability Power) magic damage in a line. If a unit bleeding from the Zero Energy Lance is damaged, Rix'Khan will refresh any temporary movement speed buffs he has active.

R (Ultimate) - Dominance of the Void Cost: 100 mana / Cooldown: 140/120/100 seconds
Rix'Khan forces the full power of the Void upon target enemy champion dealing 150/225/300 (50% Ability Power) (50% of bonus AD) magic damage. If Dominance of the Void kills its target, Rix'Khan will siphon its remaining life force, regenerating 20% of that target's maximum health and half as much as mana over six seconds.

I will continue to update this thread. What do you guys think of his name? Does he have too much CC for an assassin? Does he need more mobility instead? Is his ultimate not good enough, boring, OP? Feel free to give you feedback.

EDITS:

1. Changed W scaling from (45% bonus AD) to (50% total AD) for proper damage for an AP build.
2. Changed Ultimate cooldown from 120/105/90 seconds to 140/120/100 seconds. Changed text from "If Dominance of the Void kills its target, Rix'Khan will immediately enter stealth for three seconds." to "If Dominance of the Void kills its target, Rix'Khan will siphon its remaining life force, regenerating 20% of that target's maximum health and half as much as mana over six seconds." This rewards Rix'Khan with enough sustain to continue fighting after successfully killing a target.