Yuki-Onna

Infect. (This creature does damage to creatures in the
form of -1/-1 counters and to players in the form of
poison counters.)
{b}{b}{b},{t} Exert Yuki-Onna: All creatures able to
block Yuki-Onna this turn, must do so.
(An exerted creature won't untap during your next
untap phase).