Azorius Locket

A fixing artifact that fixes early is dead weight late, and this cycle folds a second life into itself to solve exactly that. The three-mana front half is deliberately unexciting: a rock that taps for either guild color and does nothing cheaper fixing couldn't. The payoff is the sacrifice mode, which turns the rock back into resources once you've flooded past needing it. Note the shape of that activation: four hybrid pips of white-or-blue, so the drain scales with how committed you are to the guild's colors, wanting you deep enough into WU to pay it comfortably rather than splashing a third color. Everything about the card turns on the curve. In the opening turns the Locket smooths your draws; by the point where a lone mana source is a topdeck you'd rather not have, it converts into two cards and clears itself off the board. That self-cannibalizing structure is what separates it from the flat Signet-style rocks it superficially resembles: those stay rocks forever, while the Locket is built to be spent. It is a plainly utilitarian card, engineered for slower two-color decks that expect to reach a late game where raw card advantage matters more than the acceleration it provided on turn three.