Battleground Burial Mound

Whenever a creature you control dies, exile it
under Battleground Burial Mound until it leaves
the battlefield. (When Battleground Burial Mound
leaves the battlefield, put those cards into their owner's graveyard.)
Pay 1 life, {t}: Add {b}.
{t}, Sacrifice Battleground Burial Mound: Add {b} for each creature card exiled under
Battleground Burial Mound.