Reef Slagheap enters the battlefield tapped unless you sacrifice a Merfolk.

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

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

: Reef Slagheap becomes a 1/1 blue and red Merfolk creature with first strike until end of turn. It's still a land.