The Shapeless Isle

The Shapeless Isle enters the battlefield tapped unless you control a Servant Rider creature.
{t}: Add {w} or {u} to your mana pool.
{3}{u}, {t}: Tap target creature. It doesn't untap during its controller's next untap step.
A ruined temple and the roar of the tides was all the island possessed, but that silence was enough for the three sisters who quietly passed the time together living there.