Icefang Naga

Morph {2}{u}
When Icefang Naga is turned face up, tap target creature. It doesn't untap during it's controller's
next untap step.
Submerge — {1}{b} (Exile this card and up to one
other face down permanent in a face-down pile.
Shuffle them, then return those cards to the battlefield
face down. Submerge only at any time you could cast
a sorcery.)