Curse Devil

Summoning the Curse Devil calls up a huge two-headed skeleton crowned with horns. One skull keeps a human cast, while the other bears a trio of eye slits and elongated, mandible-like fangs. Clawed hands hang from its frame, and a swollen, distended ribcage juts out from its body. When it merely speaks, the manga renders it as a pair of dark lips or an enormous mouth floating in shadow, whereas the anime instead plants the creature bodily behind whomever it addresses.

Nothing of the Curse Devil's inner character has been revealed across its appearances.

Like every devil it holds the standard set of devil traits, but as a contract devil its real value lies in the bargains it grants. The heart of these is its curse: once a contractor drives a nail into a victim the required number of times, the skeleton materializes, hoists the target up with arms spread wide, and tears into their shoulders and neck while wringing their limbs.

Aki Hayakawa pays for the power with slices of his own lifespan, cursing a foe by stabbing three times and barking "Fire!" as a spectral finger flicks the nail; he learns afterward that the deal has left him roughly two years to live. Santa Claus instead trades away the feeling in several fingers for a four-stab version, and crucially the stabbing need not be done by the contractor, since the curse triggers even when Tolka delivers the final blow. The devil can also hide itself from sight, so that when it killed Denji neither he nor Beam could perceive it, leaving him to appear crucified in midair. Its lethal work shows throughout the story: Aki uses it to lift and bite Katana Man to death, and Tolka's nail-trap later sends the Curse Devil to fatally maul Denji.