The Blue Serpent was an enormous ocean-dwelling creature. It obeyed the commands of the Blue Priest and of Hera. It swallowed Deianeira and Hercules when they were en route to Troy and Hercules killed it by crawling through its body and wrapping himself around the serpent's heart until it stopped beating. Although impressive, the Blue Serpent was not the most dangerous sea creature who served Hera: Perfidia was larger and could make limited forays onto land, something the Blue Serpent seemed incapable of.