Athiophel (meaning "brother of foolishness") was a grandfather-in-law and chief adviser to King David during his reign, and was renowned for his wisdom throughout all Israel . He committed high treason against the King when he became an adviser to Absalom declared himself King of Israel.
During a council of war, Athiophel wisely advised Absalom to pursue David through the night, capturing his women . Hushai the Archite, acting as a double agent for David, told Absalom to gather up a larger force to overtake David's men.  While this would seem sound advice, this was really to distract Absalom while David's forces further prepared for combat.
Athiophel saw through this lie, and realized that he had chosen to follow a conceited fool instead of following a wise King. Knowing his eventual fate if he continued living, he left Absalom's meeting, and returned home to Giloh . He then arranged his will, hanging himself afterwords. Following his death, Athiophel was buried in his ancestral tomb .