Nuukrasil's Nightwalker

Nuukrasil's Nightwalker's power is equal to the
number of creatures you control.
{x}, {t}: gain control of target creature with
converted mana cost X or less, it gains haste,
return it to its owners hand at the beggining
of their end step.
The Nightwalkers were the first to appear, signalling
doom for the entire plane