Rotted Catacomb

({t}: Add {b} or {g} to your mana pool.)
Rotted Catacomb enters the battlefield tapped.
When Rotted Catacomb enters the battlefield, reveal the top card of your library. If
it's a land card, untap Rotted Catacomb.
"The underground is a dark place. That much is certain. Full of foul creatures best avoided."