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Biomass Mutation

Card Name

Biomass Mutation

Mana Cost

X

Type

Instant

Rarity

Rare

rules Text

Creatures you control have base power and toughness X/X until end of turn.

Flavor Text

"A regression to ancient forms? A glimpse of future evolutions? Or a fleeting alteration of the present?" —Vorel of the Hull Clade

Legal Formats

Commander, Legacy, Modern, Pioneer, Vintage

Not Legal Formats

Alchemy, Brawl, Explorer, Historic, Pauper, Standard

Rulings

(1/24/2013)
Choosing 0 as the value for X will likely cause creatures you control to become 0/0 and be put into the graveyard.
(1/24/2013)
Biomass Mutation overwrites any effects that set the power and/or toughness of a creature you control to a specific value. Effects that modify power and/or toughness but don't set them to a specific value (like the one created by Giant Growth), power/toughness changes from counters, and effects that switch a creature's power and toughness will continue to apply. For example, say you control a 1/1 creature that's getting +4/+2 from an Aura, has a +1/+1 counter on it, and is affected by an effect that switches its power and toughness. This creature is 4/6. If you cast Biomass Mutation with X equal to 4, the creature would become 7/9 (4/4, +4/+2 from the Aura, +1/+1 from the counter, then switch power and toughness).