Priam was king of Troy during the Trojan War. His son Paris (one of 50 sons and many daughters) caused the Trojan War, while his daughter Cassandra predicted it. Priam was killed during the Sack of Troy.
The quote is from Shakespeare’s King Henry IV, Part II (Act I. Scene 1):
Such a man, so faint, so spiritless,
So dull, so dead in look, so woe-begone,
Drew Priam’s curtain in the dead of night,
And would have told him, half his Troy was burn'd.