The Council of Ancients were a clan of wise, long-lived predators that ruled supreme over other clans for a certain duration of time. They ensured that the laws of the race were followed, certain rituals and traditions were adhered to, and decreed rewards and punishments for both individuals and entire clans. The Council of Ancients also gives clans hunting rights to planets and presumably all clans need such permission before they begin a Hunt. Instead of sustaining itself naturally through breeding, the Council of Ancients chooses a clan to succeed itself. It does this by weeding out all the "weaklings" through a series of gruelling trials, including Xenomorph hunts and deliberately set-up Clan-Clan disputes to determine the superior clan. Presumably, however, these trials vary with the current council.