This is probably a bad idea but I like the other infinite stack champions (champion idea)

Passive: Gain 1 health per 10 bonus mana and 1 mana per 10 bonus health. Doesn't stack with itself.

Q: Infantium reaper: (placeholder)'s next basic attack deals 20 bonus physical damage plus a portion of his health and mana in bonus physical damage.

Q Passive: If Infantium reaper kills a unit it's cooldown is halfed. Infantium reaper's cooldown is refunded outright on takedowns.

Damage: 20+100% physical damage + 10% bonus health + 10% bonus mana Mana cost: 20/25/30/35/40 + 1/2/3/4/5% current mana Cooldown: 14/12/10/8/6 seconds

W: Darkness style: (placeholder) can toggle this ability to switch between red or blue mode. Additionally enemy champions attacked by (placeholder) gain 1 mark of darkness every time they are hit by his basic attacks stacking up to 5 times.

Red: (placeholder)'s basic attacks consume 2/4/6/8/10 health but deal 5/10/15/20/25 + 5% ad ratio bonus physical damage.

Blue: (placeholder)'s basic attacks consume 2/4/6/8/10 mana but deal 5/10/15/20/25 + 5% ap ratio bonus magic damage.

W passive: If Infantium reaper kills a unit (placeholder) gains 2/4/6/8/10 bonus health/mana depending on whether red or blue mode was the active mode.

Red mode Health cost: 2/4/6/8/10 health Blue mode Mana cost: 2/4/6/8/10 mana Red mode bonus physical damage: 5/10/15/20/25 + 5% ad Blue mode bonus magic damage: 5/10/15/20/25 + 5% ap Infantium reaper bonus health/mana: 2/4/6/8/10 Cooldown: .5 seconds

E: Versaterror: (placeholder) does one of two effects depending on which direction he is facing in relation to nearby enemy champions. The effects are empowered by stacks of darkness on the nearby champions.

If facing toward an enemy champion: Devour all stacks of darkness on the targetted enemy champion to gain 5/7/9/11/13 movement speed for each stack.
If facing away from an enemy champion: Cripple the targgetted enemy champion to slow the target by 5/7/9/11/13 movement speed for each stack of darkness.

Movement speed increase/decrease: 5/7/9/11/13 Range: 800 Cooldown: 25/24/22.75/21.5/20 seconds Mana cost: 70/75/80/85/90

R: Cresent slash of doom: (placeholder) slashes a large area dealing aoe physical damage, bonus magic damage for every stack of darkness, while leaving a large cresent of darkness for 5/7.5/10 seconds. Enemies inside the cresent gain 1 mark of darkness every half second and are slowed by 10/20/30% for 1 second re-applying every .5 second.

Damage: 200/375/550 + 100% ad ratio + 20% bonus health ratio + 20% bonus mana ratio (+100 magic damage per stack of darkness) Debuff apply delay: every .5 seconds Slow: 25% mark: 1 per debuff Cresent duration: 5/7.5/10 seconds