The Weapon, sometimes referred to as Cortana 2.0 (SN: CTN 0563-8), is an advanced, next-gen artificial intelligence construct created by the UNSC to serve as the successor to John-117's original AI companion Cortana. Originally designed for a singular goal, Weapon's existence took a drastic turn upon her meeting the Master Chief and she took to fulfilling a much larger and more long-term mission.
The Weapon was designed and created by Dr. Catherine Halsey in order to mimic the security of Installation 07 (Zeta Halo). The main purpose of The Weapon was to trap Cortana, following her descent into Rampancy, so that she could be retrieved and deleted. It is never specifically stated as to exactly when The Weapon was created but it is known that she was transported to the Ring World by the UNSC Infinity and was present on the surface of Zeta Halo during the attack on the UNSC Infinity by the Banished, a sect of Brutes, Elites and other related species who had broken away from the Covenant prior to the war.
Upon meeting her predecessor on Zeta Halo, The Weapon was able to successfully contain Cortana who, seeking to redeem herself in the eyes of the Master Chief, put up no resistance against the younger AI and instead surreptitiously tampered with The Weapon's automated self-deletion protocol that had been put in place to activate once Cortana's deletion was either achieved or no longer possible. Cortana then detonated a large chunk of the Ring, killing herself and the Banished leader Atriox who had sought to exploit both her and the Ring. As a result, The Weapon suddenly found herself living a purposeless existence and unable to self-delete. As a further precaution, before her death Cortana erased all evidence of her tampering and the circumstances of her death from The Weapon's memory.
For six months, The Weapon remained alone on the surface of Zeta Halo, waiting for the Master Chief to retrieve her whilst hiding within the systems of the Forerunner surface installations. It was then that the Master Chief was finally awoken and returned to the Ring's surface to continue the fight against the Banished. In the course of his operations, the Master Chief encountered The Weapon and questioned her on Cortana's status. The Weapon confirmed Cortana's deletion but could not remember who was responsible nor explain how she herself was still operational. She then requested that she be deleted in accordance with her programming but John refused, saying that the fight was not over, confusing The Weapon further. Informing her that "the missions change, they always do.", John presented his suit's empty AI-interface chip; The Weapon gladly transferred herself into it and from that point became the Master Chief's new official AI companion.
It appears that the Weapon is a "Dumb" AI, based on her sole mission to secure the ring and lack of knowledge of the Banished on Zeta Halo. This can be compared to the "Smart" AI Cortana's many capabilities and extensive knowledge on a multitude of subjects. (Source)
- Halo Infinite (First appearance)