Krark's Thumb

Coin-flipping in Magic is a fringe mechanic precisely because it hands half your outcomes to chance, and this is the card built to bend that math without removing it. Flip two, keep the better, and a 50/50 becomes 75/25 in your favor: the arithmetic is the whole appeal, and it compounds across cards that flip repeatedly until you lose. The "ignore one" clause is doing the structural work; it does not require the flips to be sequential or independent of each other, which is what lets a single Thumb chain cleanly through a card that asks for flip after flip. The "if you would flip a coin" wording is just as load-bearing in the other direction: the replacement keys off your own flips, so an opponent's copy never lends you a third coin, and the legendary type line caps how many of yours can sit on the battlefield at once. What lifts it above novelty is the breadth of the win-on-flip catalog it points at: every "flip a coin, if you win" card in the game suddenly reads as "do the thing, probably." Build around chance and Krark's Thumb is the piece that stops the deck from being a coin toss and starts making it a near-guarantee, the closest Magic comes to letting you weight the dice while keeping the dice on the table.