Castor (CASS-ter). Mortal brother of the immortal hero Polydeuces, together the Dioscuri or Hero Twins. Polydeuces was considered godly enough to be admitted to heavenly Olympus, while his brother was dispatched to the Underworld as a mere mortal. But Polydeuces interceded on his twin's behalf, on the plea that he could not bear eternal separation. The gods relented to the extent that the two were allowed to remain together forever, spending half the year deep in the earth beneath their shrine in Sparta and the other half on Olympus.