Oni, The Demonic Archangel

Oni, The Demonic Archangel "Hell didn't choose me, I chose Hell" "I shall purify the world with the power of The Demon"

Passive: Double-Edged Potential +For every 10 seconds, Oni marks an Enemy Champion with the Million-Mile Stare for 3 seconds. Enemy which is affected will receive 30% extra damage from Oni's basic attacks and abilities but Oni loses 5% of his Maximum Health each time he attacks the target. +Upon dropping below 35% health, Oni sacrifices another 10% of his Maximum Health to gain 100% Attack Damage, Life Steal, Spell Vamp, Attack Speed, Movement Speed and Cooldown Reduction for 5 seconds or until he reaches 60% health. (this will not activate if Oni is below 20% health) (75 seconds cooldown)

Q: From The Fiery Depths of Hell Cost: 35/50/65/70/85 Health Oni corrupts an area with searing power, dealing 50/80/100/120/150 (+0.2 AD) to 80/110/150/175/200 (+0.4 AD) magic damage for 3 seconds based on the enemies' missing Health. Enemies in the area are slowed by 35%.

W: Doom and Demise Cost: 40/55/69/75/80 Health Oni possesses an enemy Champion and dashes to it, dealing 5/15/20/50/75 true damage and marks it with the D-Mark for 2 seconds. The target will be affected by Grievious Wound and slowed by 35/37/40/50/60% for 2 seconds. At the end of the D-Mark, it will receive Magic Damage equal to 5/7/8/9/9.5% of its Maximum Health

E: Skewer The Guilty Cost: 50/70/75/80/95 Health Oni summons tridents of Hell from the ground, dealing 90/110/130/150/160 (+0.4 AP)(+0.2 AD) magic damage and knocks enemies into the air.

R: Gift of Satan Cost:10/15/20% of Current Health Oni turns himself into a living weapon and explodes, dealing 250/325/350 (+0.75 Bonus AD)(+0.3 AP) to 425/475/550 (+1.5 AD)(+1 AP) physical damage to all enemy units caught in the explosion, based on the distance of the unit. If Gift of Satan affects Oni's allies, it will instead heal them for the same amount of minimum damage. Oni will receive a bonus of 25/30/35% Armor, Magic Resistance and Health Regen for 4/5/6 seconds after the explosion.

Update 1: I tuned the damage down a lil' bit and removed the silence from W since Slow+Silence=Broken. Also, I want this guy to sacrifice a part of himself to cast spells so I also added the health cost for each spell. Last but not least, I have made some major (or maybe minor) changes in his ult. Thx