(from Greek dioskouroi, sons of Zeus) Twin gods of ancient Greece and Rome. They aided shipwrecked sailors and accepted sacrifices for favourable winds. Castor was mortal and Pollux was immortal; when Castor was killed, Pollux disowned his immortality to join his brother. The pair were excellent horsemen and were said to have participated in the hunting of the Calydonian boar, the voyage of the Argo, and the rescue of their sister Helen (who had been captured by Theseus). They were believed to have aided the Romans in an important battle early in their history, and a temple in their honour was built in the Roman Forum.