Amulet of the Vengeful: Every kill adds 1 charge buff to your character. Maybe like, 1% bonus to all damage per charge, maximum of 20 charges. At 20 charges, the next kill you receive summons demonic vengeful spirits who return to claim their amulet, and attack you until you kill them. When you kill them, the damage multiplier is DOUBLED for 8 seconds, then you lose all charges. Also, the vengeful spirits deal damage relative to your damage (think like, set dungeons).
It doesn't have to be these exact numbers, but I feel the idea of an item that summons monsters to attack you for using it could spice up the gameplay for season 7!