Support/Assassin Champion who deals temporary damage?

It would be cool if there was a champion who dealt a large amount of temporary damage, or partially temporary damage. Like if they applied Tahm Kench's Grey Health onto enemies. They could then deal a ton of damage but would have to continuously apply it so it doesn't revert and their allies can finish the kill.

Thematically, a ghost champion or a champion from the Shadow Isles would fit the bill. I could also imagine Lulu or someone from the Fae doing something similar (if she can give allies Health and size, maybe she can reduce Health and size as well?).