Darya, the Chilling Frost

Exile a creature named Darya, Novice Summoner and an Elemental creature you control: Cast Darya, the Chilling Frost from your library.
At the beginning of each upkeep, if you control no Elemental creatures, create a 3/3 blue Elemental creature token.
Sacrifice an Elemental: Tap target creature. It doesn't untap during your next untap step.