What was Calchas in Greek mythology?

Calchas or Calchantas from Mycenae or Megara, was one of the most famous seers of Ancient Greece. A famous oracle, he interpreted the future, a gift given to him by the God Apollo, as he was the son of Thestor, who was a descendant of the god.

His name is etymologically derived from the word kalcha (purple dye), meaning "the purple, the mournful", or from a transposition of the "x" with the "k" in Halkas -> Calchas, meaning "the bronze man".

Calchas, with his prophecies, played an important role in the war and the abandonment of Troy, as at every important moment of the war and its preparation, we find a prophecy of his.