Roar of Skithiryx

(You may cast a legendary instant
or sorcery only if you control a legendary
creature or planeswalker.)
Put a -1/-1 counter on up to three target
creatures without infect or deathouch.
Target creature gains infect until end of
turn. (It deals damage to creatures in the
form of -1/-1 counters and to players in the
form of poison counters.)