Carry Away

Theft works by attacking the wrong noun. Most steal effects in blue and red target the creature; this one targets the gear. Enchant the Equipment, and the moment the Aura resolves it pops loose of whatever creature was holding it and changes hands, after which you can bolt it onto something of your own. The trick is that Equipment, unlike a creature, never minds whose army it serves. A stolen Sword does not have summoning sickness, does not get returned at end of turn, does not phase back; it is now yours, permanently, and it will keep being yours as long as the Aura stays put. That permanence is the design tension Carry Away resolves: blue gets to keep an artifact for good rather than borrow it for a turn, paying for that durability with the same vulnerability every Aura carries. Destroy the Aura, or destroy the Equipment, and the deal unwinds. The narrowness is the cost: in a board with no Equipment worth stealing, the card is a dead two mana, which is why it lived and died with whatever artifact density the format around it happened to support. It is a precise answer to a specific worry (the opponent's busted piece of gear) rather than a flexible removal tool, and it reads as an artifact-block curiosity because that is exactly what it was built to be.