Legacy Weapon

Pay one of every color and exile a permanent: that is the whole machine, and because no tap symbol gates it, the only ceiling on repetitions per turn is how much WUBRG the manabase can churn out. Exile is the cleanest answer the game has, indifferent to regeneration and indestructibility, and "target permanent" is the widest possible scope of what the activation can point at. The one wall it cannot climb is protection from targeting: hexproof and shroud stop it cold, because every use demands a legal target. Then there is the refusal to die. Mill it, discard it, destroy it, and it shuffles itself back into the deck instead of resolving into a graveyard, so the only durable way to be rid of it is exile or theft. Put those two properties together and you have an attrition-proof closer for a deck that already produces all five colors and lacks only a finisher that cannot be ground away: once the mana is online, it dismantles the board one permanent at a time and cannot itself be answered through trades. The cost is the leash, demanding a manabase whose entire job is enabling five colors, which is exactly why it suits rainbow control shells wanting a win condition immune to the usual grind. The flavor matches the engineering: a singular device whose whole identity is that it answers everything and outlasts everything, provided you can pay the toll in full.