Trychophya, Fen Keeper

When Trychophya, Fen Keeper enters the
battlefield, put the top three cards of your
library into your graveyard.
{b/g}{b/g}{t}: Exile up to three cards from your
graveyard, then create a 0/0 plant token with
defender and put X +1/+1 counters on it, where
X is the number of cards exiled this way.

The fen will keep them safe for life. Their debt will be
paid once they're gone.