Ruin of Emrakul

Ruin of Emrakul enters the battlefield tapped.
When Ruin of Emrakul enters the battlefield,
Tap target land an opponent controls. It doesn't
untap during its controller's untap step for as
long as Ruin of Emrakul remains tapped.
You may choose not to untap Ruin of Emrakul
during your untap step
{t}: add {c}. ({c} represents colorless mana.)