A (kind of twisted) concept for a passive: Internal Demons

Passive - Internal Demons: Horrifying creatures called Internal Demons wander the rift. Only [Champ Name] can see them. There are 4 different kinds of Internal Demons. These creatures will hover near [Champ Name] and she/he can attack them. Whenever these creatures attack, [Champ Name] will lose Sanity instead of taking damage. Killing them grants a buff/enhancement to [Champ Name] depending on which Internal Demon was killed.

Creature 1: [Insert Buff 1 here] Creature 2: [Insert Buff 2 here] Creature 3: [Insert Buff 3 here] Creature 4: [Insert Buff 4 here]

[Champ Name] has a unique resource called Sanity. She/he starts the game at a certain amount. She/he can only recover Sanity by being near allied champions. As her/his Sanity lowers, [Champ Name] has greater damage output but becomes more Fragile and the Internal Demons hover closer to her/him. If she/he reaches 0 Sanity, the Internal Demons begin attacking her/him, draining her/his health for at least a few seconds. After the few seconds, [Champ Name] can walk over to an allied champion to recover some Sanity and stop the onslaught of the Internal Demons.