In the Twelve Labors of Hercules, Poseidon was associated with sending the Cretan Bull.
The bull emerged from the sea as a sign connected with Poseidon and was given to King Minos of Crete. Minos was expected to sacrifice it, but he kept the magnificent animal instead. As punishment, Poseidon caused the bull to become wild and destructive. Hercules later received the task of capturing it alive as his seventh labor.
The myth of the bull overlaps with the story of Theseus, who later faced a bull in the region of Marathon. Ancient and later writers sometimes treat the Cretan Bull and the Marathonian Bull as the same creature, while other accounts separate them. Poseidon’s connection concerns the bull’s divine origin and Minos’s failure to sacrifice it.