Satella

Whenever a card is exiled, including Satella herself, put a +1/+1 counter on Satella. Satella never loses +1/+1 counters, regardless of zone changes or game effects. Whenever Satella destroys a creature, exile that creature. If Satella would die, exile her with all counters on her instead. You may cast her from exile for {B}{B}{B}.