Mantis, Calmer of Minds

At the beginning of your upkeep, you may
pay {x}{u}. If you do, tap up to {x} target creatures.
They don't untap during their controller's next
untap phase.

{1}{u}{u}{t}: Gain control of target creature with toughness 2 or less.
{1}{u}{u}{u}{t}: Exchange control of two target tapped creatures you don't control.