Nomad Caves
Land (Rare)

At the beginning of your end step, if you didn't cast any spells this turn, Nomad Caves deals 1 damage to you.

Tap: Add W or B to your mana pool.

Sacrifice Nomad Caves: Add W or B to your mana pool.

1W: Nomad Caves becomes a 0/4 white and black Citizen creature with defender until end of turn. It's still a land.

Douglas Walker