Prologue to Phyresis

Prologue to Phyresis is legal in every relevant format but Commander is where it actually earns a slot. In Pauper infect or proliferate strategies it's a clean one-mana spell that advances multiple angles at once, but those decks are fringe. In Modern and Pioneer, dedicated poison strategies exist but are narrow enough that Prologue to Phyresis competes with faster, more aggressive infect payoffs and rarely makes the cut outside of niche proliferate shells. Commander is the true home: multiplayer means hitting three opponents simultaneously is vastly more impactful than in any one-on-one format, and the proliferate synergy commanders in the format — Tekuthal, Inquiry Dominus chief among them — give it an engine it simply doesn't have elsewhere.