Grip of the Roil

Oracle Text

Surge 1U (You may cast this spell for its surge cost if you or a teammate has cast another spell this turn.)

Tap target creature. It doesn't untap during its controller's next untap step.

Draw a card.

Card Rulings

1/22/2016 Grip of the Roil can target a creature that’s already tapped. It still won’t untap during its controller’s next untap step.
1/22/2016 Grip of the Roil tracks the creature, but not its controller. If the creature changes controllers before its first controller’s next untap step has come around, then it won’t untap during its new controller’s next untap step.
1/22/2016 For some cards, surge represents only an alternative cost, a discount that applies if you or a teammate has cast another spell this turn. Other cards, like Reckless Bushwhacker, have additional abilities or effects if you paid the surge cost to cast the spell.
1/22/2016 The other spell that you or a teammate cast can be one that’s resolved, one that was countered, or (for instants with surge) one that’s still on the stack.
1/22/2016 If an instant or sorcery spell cast for its surge cost is copied, the copy is also considered to have had its surge cost paid.
1/22/2016 Casting a spell for its surge cost doesn’t change its mana cost or its converted mana cost.