Crown of the Apocalypse

The Crown of the Apocalypse is a demonic artifact which manifests over Hellboy's head repeatedly, usually while his horns are regrowing (for example, when Hecate transported him to the Ogdru Jahad's prison). After Igor Bromhead bound Hellboy, the demon Ualac stole the crown and wore it, temporarily becoming the Beast of the Apocalypse. Hellboy defeated Ualac and turned him over to Astaroth, who said he would keep the crown in Hell until Hellboy came there to take up his father's ring and sword.

The crown left Astaroth's possession while Hellboy was fighting a group of giants. Hellboy went on a violent rampage and slaughtered them all viciously, causing the crown to reappear over his head. It vanished after he broke off his horns, leaving it's current whereabouts unclear.