The Undertaker

At the beginning of your upkeep, if
The Undertaker is in your graveyard, you may pay {p/b}{p/b}. If you do, return The Undertaker to the battlefield.
When The Undertaker returns to the battlefield
from your graveyard, Amass Druids 1.
(To amass Druids 1, put a +1/+1 counter on an
Army you control. It's also a Druid. If you don't
control an Army, create a 0/0 Black Druid Army creature token first.)