Cold-Eyed Selkie

The whole engine hangs on a contradiction the card cannot resolve by itself: islandwalk guarantees the hits only when the defender controls an Island, but the card-draw payoff scales with the body's power, and a 1/1 draws exactly one card a turn. The hybrid green-blue mana lets either half of the Simic pairing cast it, which is the tell for how it expects to be used: green pumps the body, blue supplies the evasion target. Equip it, enchant it, give it a counter or two, and the islandwalk turns into a guaranteed refill clock that scales linearly with whatever you spent making it bigger. Against a deck with no Islands, it is a 1/1 that does nothing relevant. That binary is the design honesty here: the reward is enormous and conditional, and the condition is entirely out of your control. Plenty of unblockable-by-landtype creatures carry combat-damage triggers, but most of those care about milling or burning, slow ways to leverage evasion; this one converts a connection straight into cards, the cleanest possible advantage, so it functions as a build-around rather than a beater. The Merfolk Rogue line is incidental. What matters is that it was built for a deck willing to invest mana in its power and lean on a metagame full of blue, where the islandwalk almost never goes dead.