Skeletal Grimace

The trade an Aura always asks you to make is tempo against permanence: you spend a card to buff a creature, and if that creature dies you lose two cards to their one. This one answers that math directly. The regeneration shield it grants is the insurance policy on the investment, turning the enchanted creature from a removal magnet into something that survives combat and most targeted kill spells, with mana left over each turn to keep regenerating. The +1/+1 is almost incidental; the real value is the persistence, which converts a vulnerable two-card commitment into a recurring threat that grinds through attrition. Cheap black Auras of this stripe exist to keep one creature alive across many turns rather than to inflate its stats, the kind of design that pays off when a single well-protected attacker matters more than a wide board. The friction is the one every regenerator inherits: regeneration is a replacement effect that only intervenes on destruction, so it answers spot removal and lost combats cleanly but does nothing against exile, against bounce, against a -X/-X that shrinks the creature to death, against anything that removes the threat without trying to destroy it. But against the targeted kill and chump-blocking that defines most ground stalls, a creature wearing this becomes genuinely hard to deal with, and the open black mana to feed it is a low enough tax that the protection rarely sits idle.