Tidewalker

Vanishing is usually a tax: you get a discounted body in exchange for a built-in expiration date, and the time counters tick toward a forced sacrifice no matter what you do. This one inverts the math. The counters aren't a leash on the body; they are the body. Power and toughness track the count exactly, so a creature that enters reading off your Islands starts large and shrinks one point each upkeep until it dissolves. It rewards a dense mono-blue manabase the way few three-drops do, scaling with land count rather than spell quality, but the same vanishing clock that makes it enormous guarantees it can never be a permanent threat: the bigger it lands, the more upkeeps you must survive while it bleeds out, and there is no way to refuel the counters once they start falling. The result is a finisher with a public, ticking deadline, the rare creature whose stat line is legible to both players as a countdown. As a piece of mechanical translation it takes a keyword built to balance undercosted bodies and reroutes it into a payoff for committing hard to a single color, then prices the payoff in inevitability rather than mana.