against the Didact, a rogue Forerunner who hates humans. Cortana sacrifices herself to save the Chief and stop the Didact's plan. Cortana's survival is revealed in Halo 5, when she calls Master Chief to the Forerunner world Genesis. Cortana explains she survived the destruction of the Didact's ship and her own rampancy by entering the Domain, an ancient repository of knowledge. Granted an infinite life span by the Domain, Cortana believes that she and other AI (the "Created") should enforce peace through the galaxy. Cortana begins using ancient Forerunner constructs known as Guardians to enforce the Created's will throughout the galaxy. In Halo Infinite, Master Chief travels to the ringworld Zeta Halo and recovers the Weapon, a copy of Cortana designed to contain her for deletion. Traveling across a damaged Halo's surface and fighting the enemy faction known as the Banished, the pair recover data fragments left behind by Cortana that fill in what occurred six months earlier; Cortana threatened the leader of the Banished, Atriox, and destroyed his homeworld when he did not submit. In retaliation, a vengeful Atriox used the Weapon to capture Cortana, informing her that the Banished had already defeated the UNSC and Chief, and orders Cortana to surrender the ring to the Banished (as their new home). Realizing she was defeated by her own copy and believing the Chief to be dead, Cortana finally realizes her mistakes. In attempt to stop Atriox from uncovering the ring's secrets, she sacrifices herself again to atone for her actions, severely damaging the ring, deactivating all Guardians and preventing the Banished from activating it; this also sends Atriox to his apparent death, though he is later revealed to secretly have survived. In a final message, Cortana apologizes to Chief for her actions and encourages him to trust the Weapon as a new partner. Other appearances Cortana's first appearance in the Halo franchise is in the novel Halo: The Fall of Reach, a prequel to the first Halo game. Dr. Halsey allows Cortana to choose which SPARTAN-II soldier to accompany on an upcoming mission; Cortana picks the Master Chief, whom she believes is her best match. Cortana helps the Master Chief to survive the near-lethal exercises designed to test the Chief's armor. Afterward, she plants incriminating evidence in the files of Colonel Ackerson, the operative who nearly killed both of them, as revenge. Cortana makes a small appearance in 2010's