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

Biomass Mutation

Creatures you control become X/X until end of turn.

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

Secrets of Strixhaven Commander

Duskmourn: House of Horror Commander

Vault 87's Evolutionary Experimentation Program exposed subjects to an airborne version of FEV. Rapid physical enhancements accompanied sharp mental regression, and the oldest mutants would become almost feral.