Slipstream Elemental

Relay 1 (As an additional cost to cast this
spell, exile two nonland permanents you
control. Return it to the battlefield at the
beginning of your next upkeep. Creatures
returned this way gain haste until end of
turn.)
Whenever another creature enters the battlefield
under your control, you may tap target creature.
That creature does not untap during its
controller's next untap step.