Xathrid Demon

A 7/7 flier with trample for six is a finisher rate any era recognizes, but the upkeep clause turns the body into the cost of a Faustian bargain. Each turn it lives, you owe a creature: sacrifice one and your opponents bleed for its power, or the demon taps itself and takes seven out of your own life total. That second branch is the tell. This is a closing piece that punishes the empty board, so it asks you to keep a stream of expendable bodies on the table rather than just slam it as a top end. The drain scales with the sacrificed creature's power, which quietly invites you to feed it something fat rather than a token, and the "creature other than this creature" wording means the demon can never eat itself to dodge the upkeep. It belongs to the old tradition of black fatties that bill you for the privilege of attacking with them, the Juzám Djinn and Phyrexian Negator school where the drawback is the design rather than a footnote on it. The difference is that those cards bled you passively; this one hands you the knife each turn and dares you to keep a sacrifice engine fed. Left alone on an empty board, it is a seven-life clock pointed at its own controller, which is exactly the friction that pays for a flying, trampling seven-power threat at this cost.