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

: Add  to your mana pool. Activate this ability only if you control a Swamp.

: Add  to your mana pool. Activate this ability only if you control an Island.

: Rotting Coliseum becomes a 2/2 blue Merfolk creature until end of turn. It's still a land.