Poisonous Gas

Creatures you control have deathtouch.
Creatures you control with deathtouch from
another source gain double strike. When a
creature you control with both deathtouch and
double strike deals damage to a player, you
may sacrifice it. If you do, add {x} to your mana
pool, where X is the cost paid when Poisonous
Gas was cast plus the damage dealt to opponents
by this creature this turn.
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"Don't inhale." —Halt Farantul