Scion of Stygia (Adventures in the Forgotten Realms)

Creature Ñ Tiefling Shaman - Flash
Cone of Cold Ñ When this creature enters, choose target creature an opponent controls, then roll a d20.
1Ñ9 | Tap that creature.
10Ñ20 | Tap that creature. It doesn't untap during its controller's next untap step.