Flame-Kin War Scout

A landmine wearing a body. The trigger is the catch: it fires on any creature entering, including your own, so this is a 2/4 that cannot share the battlefield with a freshly cast blocker or a token without detonating itself. That indiscriminate clause is the whole bargain. Four damage will kill most midrange bodies, and the scout asks you to hold up that threat as a deterrent, let an opponent's creature resolve, and trade your 2/4 into it on your terms. The friction runs deep: at four mana it is not cheap, and the self-immolating trigger means you rarely get to develop your own board alongside it. It wants a battlefield that has already stopped growing, which is exactly when a hard-to-kill wall does the least work. Designs that gate a removal effect behind a creature's death have appeared in many shapes since (bodies that punish the next thing to enter, deterrents that demand a sacrifice), but few tie the trigger to every entry the way this one does. That is what makes it read as a defensive wall and play as a one-shot kill spell you have to sequence around your own deck.