Seasinger

A theft engine that pays its rent in the most literal way the game allows: the 0/1 body produces nothing on its own (it taps to steal, then must stay tapped to keep what it took), and the moment your last Island leaves, the whole arrangement collapses and the Merfolk dies. The activated ability cuts in three places, and the order matters. First, a targeting restriction at the gate: you can only point this at a creature whose controller controls an Island, so the prey it was built for is a mono-blue opponent or anyone with their own islands online. Then two ongoing conditions, both of which sit with you: the steal endures only while you keep Seasinger and only while Seasinger stays tapped. Control Magic was expensive and permanent in the era this comes from, so Seasinger offered the same effect at a discount by leashing it to fragile conditions instead of buying the creature outright. Choosing not to untap during your untap step is the mechanism that sustains the steal, which means every turn you hold someone else's creature is a turn this body contributes nothing defensively. It reads as a repeatable Control Magic, but the structure is closer to a hostage standoff: a single edict, an untap-forcing effect, a land-destruction beat, or a drained blue base hands the creature back the instant any condition you depend on breaks. It is a window-merchant: cheap, recurring theft you rent rather than own.