Indulgent Tormentor

The genius here is in the loaded dice. Every upkeep, you hand the opponent a no-good-options choice: feed you a card, lose a creature, or bleed three life. None of these is a way out so much as a different flavor of falling behind, and because the trigger fires on your upkeep, the opponent is always reacting to a clock they cannot stop without dealing with the body first. That body is a 5/3 flier, which is the load-bearing restriction on the whole package: it dies to almost any burn spell and trades down to chump blockers, so the engine only runs as long as you can protect a fragile attacker. The design is a quiet inversion of the older black demon template, which leaned on drawbacks that punished you (the upkeep tax, the sacrifice clause, the "deal damage to yourself" line that ran through Phyrexian-era black). This one points the discomfort outward: the demon's appetite is the opponent's problem, not yours. The result is a creature that reads as pure upside for the controller because the cost is paid by someone else, with the only real check being how easily that fragile 5/3 falls off the table.