Loki, Lord of Trickery

Indestructible
Infiltrate (This creature can enter the battlefield
under any players control. )
Trickery 6: ( Whenever a creature gains a -1/-1
counter, put a trick counter on Loki, Lord of trickery.
When it has 6 trick counters on it, remove them and destroy each
creature with a -1/-1 counter on it. )
When Loki, Lord of Trickery enters the battlefield, you gain 6 life.
At the beginning of your upkeep, put a -1/-1
counter on another creature you control.