Herald of Torment

The life loss is the whole bargain, and bestow is how you decide what it pays for. As a creature, a 3/3 flier for three that drains a point off your own upkeep is an aggressive curve-filler with a clock pointed in two directions: theirs, and slowly, yours. The interesting part is the optionality bestow grants. Cast it as an Aura for two more mana and the upkeep tax travels with it, attaching to a creature already on the board and making it a +3/+3 flier that survives the removal spell which would have one-for-one'd a fresh body. If the enchanted creature dies, the demon falls off as a 3/3 of its own, so the card refuses to be a true two-for-one in the opponent's favor. That resilience, paired with self-inflicted attrition, is a deliberately tense package: the longer the game runs, the more the upkeep trigger matters, which pushes the card toward decks that intend to end things before their own life total becomes the liability. Demons paying a blood price for their power is well-trodden ground for black, but bestow gives this one a second mode for the same drawback, letting an aggressive deck spend the life loss on board presence early or on protecting its best threat later.