Nazoth, The Corruptor

During your upkeep, and whenever this creature attacks, choose a target non-demon creature, if that creature has 1 toughness you may take control of it. If you do, that creature now is black in addition to it other colors and is a Demon in addition to it other creature types. If the target creature has more than 1 toughness, put a -1/-1 counter on that creature.
At the beginning of your upkeep, remove a -1/-1 from all Demons you control.