Leyline of Mutation

The Leyline cycle has always been a trade: cast this thing for four mana like a normal enchantment, or start the game with it already resolved and pay nothing but a slot in your opening hand. What sits on this one is one of the strangest cost-replacement clauses in the game. Rather than accelerate a color or shield you from one, it lets you pay one of each: white, blue, black, red, and green, in place of any spell's mana cost. That is more mana than most spells cost, and every color of it, which makes the ability read as a puzzle rather than a discount. The point is not efficiency; it is reaching spells whose printed cost you cannot otherwise pay, or covering something with mana of colors it never asked for. It rewards the mana bases built to conjure WUBRG on demand: five-color rocks, treasure engines, rainbow lands that already exist to fuel exactly this kind of hoop. The turn-zero clause is what makes the payoff worth chasing, since a fixed five-color cost only helps if it lands before the game has moved past the spells you meant to cheat out. Drawn later, it is a dead four-drop enchantment idling until you have assembled a rainbow anyway. The design is a builder's card first: it asks you to solve for WUBRG, and pays out only once the solution is on the table.