Brewer's: Harmonia's Necklace
An unlucky possession, something that brings evil to all who possess it. Harmonia was the daughter of Mars and Venus. On the day of her marriage with King Cadmos, she received a necklace which proved fatal to all who possessed it.
The collar given by Alphesibea (or Arsinoë) to her husband Alcmaeon was a like fatal gift. So were the collar and veil of Eriphyle, wife of Amphiaraos, and the Trojan horse. (See Fatal Gifts.)