Dardak, Hellish Soulkeeper - (New champion idea)

I don't have any fancy bio behind this champion (lore), I just thought it was cool in my head and felt it belonged in this place.

What does he look like? In basic form a frail young man holding a set of old prison keys, wearing some old torn clothes. He walks with a stagger as if possessed. His eyes also glow red with hellfire.

Dardak Hellish Soulkeeper Assassin Weapon: Hellfire

P: Throughout various levels, Dardak's physical appearance changes to reveal his true form. With each form, he gains additional true damage with his AP. Level 4: skin/clothes from his arms fall away with only the bones remaining + 5% true damage. Level 8: skin/clothes from his legs fall away with only the bones remaining + 7% true damage. Level 12: skin/clothes from his chest/back fall away with only the bones remaining + 10% true damage. Level 16: Skin from his head falls away with only the skull remaining + 13% true damage. Level 18: Skeleton form grows to 3 times the size and is lit with hellfire, now holding a scythe + 15% true damage & 15% extra armor/ Magic resist.

Q: Marked for hell (Skillshot ). The champion throws one end of some shackles at an enemy doing on-hit damage, at a range of 700. This also marks them for 5 seconds. On-hit damage: 60/100/150/200/250 +25% AP. Cost: 40/50/60/70/80 mana Cooldown: 10/8/7/6/4

W: No Escape. Unmarked: The champion blasts a 400 unit area in a full 360 degrees around himself with a short burst of hellfire damage. Damage scaling: 50/80/140/220/350 + 60% AP. cost: 60/70/80/90/100

Marked: If the enemy is marked with your Q and within a 1750 unit range you can activate W to become a ball of hellfire and launch yourself directly at the enemy doing an on-hit slow + the unmarked damage. Slow scaling: 10%/20%/40%/60%/90%. cost: 65/75/85/95/110 Cooldown: 15/13/11/10/8

E: Hellfire. Dardak launches a beam of hellfire into the ground in front of himself, which breaks the ground up to 1000 units away knocking up any champions it runs under - doing damage. Damage: 45/60/75/100/150 + 30% AP. Cooldown: 15/12/10/8/6

If an enemy champion is marked and hit by your E, upon reaching the ground after being knocked up it is then rooted for 1.5s.

R: Condemned. A crack in the ground opens up, and a large scythe floats up into Dardak's hand. Dardak then targets an area, in which the scythe is thrown to at a range of 3500. 3 seconds later, the hand of 'The Beast' crashes through the ground with an almighty roar doing immense damage to any stood within the circle, pulling dead enemies down with it (each enemy killed with the R refunds 6 seconds off the R cooldown). If a target is marked, the scythe can be cast directly on the ground under them within the ultimates range. Damage: 400/600/800 + 100% AP Cost: 100/200/300 Cooldown: 120/180/240