Aconite
.The herb Monkshood or Wolfsbane. Classic fabulists ascribe its poisonous qualities to the foam which dropped from the mouths of the three-headed Cerbĕrus, when Hercules, at the command of Eurystheus, dragged the monster from the infernal regions. (Greek, ακóνιτoν, Latin, aconītum.)
“Lurida terribiles miscent Aconita novercæ.”