Onsos, Frozen Tyrant

When Onsos, Frozen Tyrant enters the
battlefield tap all other creatures. They don't
untap until your next untap step.
{2}{u}{u}{t}: Tap target creature, then gain control
of that creature.
Whenever 5 or more creature are tapped in a turn
you may pay {u}{u}{u}, if you do untap
Onsos, Frozen Tyrant