Mammoth Cave

When you play this land you may exile target
creature. If you do, tap the Mammoth Cave.
This land doesn't untap during its controller's
untap step as long as target creature is in exile.
Return target exiled creature to the battlefield
under its owner's control: untap this land.
{t}:Add {b} or {r}
—
I was lost, completely, hopelessly lost in the vast and labyrinthine recesses of the Mammoth Cave.
The Beast in the Cave—H. P. Lovecraft