Toxic Gas

Spells you cast mentioning "Poison," "Toxic,"
or have deathtouch cost X less to cast. At
the beginning of your upkeep, choose one-
-Creatures you control get half +X/+X
and gain deathtouch until end of turn.
-Copy the next instant or sorcery spell
you cast this turn mentioning "Poison" or
"Toxic."
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"Hold your breath." —Halt Farantul