Ghalta and Mavren

Two flagship legends fused into a single body, and the fusion is more than a novelty: the attack trigger fires off the swing rather than the cast, which is the whole point. The value is metered per combat, not front-loaded, so the 12/12 has to survive to a second and third attack to run away with a game. The two modes cut in opposite directions and reward opposite boards. The Dinosaur mode reads the greatest power among your other attackers and stamps out a tapped-and-attacking X/X copy of that number (a fresh trampling body, not a duplicate of the creature itself), which is why it wants one big threat to size off. The Vampire mode counts heads instead, minting a 1/1 lifelinker for every other creature swinging, which is why it wants a crowd. So the card is a token engine that reads your board and asks which shape it already is, then doubles down: a go-tall board leans Dinosaur, a wide board leans Vampire. The lifelink line also buys back the tempo the trample line spends, so the two halves cover each other's weakness across a long game. What holds the design together is that the trigger doesn't cost mana or ask for a card; the only resource it spends is the requirement that you commit real attackers first, which is precisely the tax that keeps a 12/12 that scales and swarms from resolving into an immediate win.