Patriar's Seal

Rainbow fixing has come attached to a legend-untapper before, but the pairing here is deliberate: the three-mana rock does its ordinary color-fixing work, then spends a mana to reset a single legendary creature you control at instant speed. That untap is doing tempo work no ordinary mana rock bothers with. It doubles a legend's tap ability inside one turn, resets a blocker after combat has already committed it, or squeezes a second activation out of a legendary creature across two players' turns at a multiplayer table. Because the untap is single-target and taxed a mana beyond the tap, it never spirals into a free loop the way an untapper with no cost attached would; every use is a considered click rather than a self-running engine. That taxed specificity is why it stays outside most decks and sits inside the narrow one it was built for: a board organized around one legend whose tapped ability earns the mana to reset it. Fixing carries the card in the early turns; the untap is the reason to keep it around late, and only if you already run a commander or key legend worth paying to spin up twice.