New Vodoo champion I have in mind. Need help tho. Comments are welcome

Hello , I play league from season 1 and I sometimes have concepts of champs and similar ones come out sometimes altho i didn't wrote them XD. So here is one. I was thinking of a "vodoo guy" that would play around ap and health bars (hes and enemies) but I didn't think of everything so feel free to comment.

Passive - gathering souls - When our vodoo master is involved in killing a enemy champion (like rengar) he gains part of their soul. Enemies with purple hp take double damage from vodoo master

Q -

W -

E - Vodoo totem -when placed , they last for 20 seconds. Enemies inside the circle around the totem lose movement speed and vodoo master heals for a portion of the damage he deals if hes inside the circle with the target.

R - Dark vodoo - Vodoo master channels for 3 seconds(like Karthus) and sacrifices 30% of hes max HP. Enemies that he has stacks on lose 30%/40%/50% of their max HP but gain it as purple HP. Purple HP can not be taken by damage but if the target loses hes green HP they die, otherwise they regain their purple HP back in 5 seconds (similar to how E of tahm kench works)