Dusky Bog

As Dusky Bog enters the battlefield, you may exile a creature or land card from your graveyard. If you don't, Dusky Bog enters the battlefield tapped.
{t}: Add {b} or {g}.
There are places on Ixalan where even the Threefold Sun does not shine. They belong only to creeping horrors and the banished worshippers of Aclazotz.