Mirrodin Besieged

Two decks folded into one permanent, sorted the moment it resolves. Choose Mirran and you get a go-wide accelerant: a 1/1 Myr for every artifact spell you cast, an engine that asks nothing of your graveyard and rewards raw artifact density. Choose Phyrexian and you get something stranger, a repeatable loot bolted to an alternate win condition that keys off fifteen artifact cards in your graveyard. The modal split is the whole design conceit, translating a faction-war conflict into a single choice made on resolution rather than a pair of separate cards, letting the enchantment lean into whichever axis your deck already runs. What makes the Phyrexian half worth building around is how quietly it stacks two independent jobs. The end-step draw-and-discard is durable card filtering on its own, valuable even in games that never cross the threshold, and it doubles as the exact tool for feeding artifacts into the graveyard the kill clause counts. Fifteen is a steep number: high enough that the win condition is a payoff for a dedicated artifact-recursion or self-mill shell rather than a stray accident, while the loot keeps the card earning its slot every turn as you assemble the pile. Mirran is the honest, immediate half; Phyrexian is the patient one that plays two games at once. One enchantment, two build-arounds, decided the instant it enters.