Calchas was the famous soothsayer of the Greeks in the Trojan war. Calchas was the son of Thestor and Mycene. He foretold the length of the siege, and when the fleet was detained in Aulis by adverse winds, demanded the sacrifice of Iphigenia. He is said to have died at Colophon, in despair at being surpassed in his art by another soothsayer called Mopsus.