Halo Infinite Ending Explained
After defeating the Harbinger in the Silent Auditorium, the Harbinger says "you have what you need. Tell them I'm sorry it took so long." Chief and the Weapon ponder who the Harbinger is speaking to, and the Weapon says that the signal is old -- really old. The Harbinger finishes by saying "The Endless will return" before dying.
The Endless are referenced a couple of times throughout Halo Infinite's campaign. It is said the Endless are "worse than the Flood". It seems the Endless are what the Banished and the Harbinger were searching for to set free.
Then, one last echo left behind by Cortana appears for another goodbye with Master Chief. Cortana says she was wrong in thinking she could do anything without Chief, because they were intended to be a team. Cortana says she understands her final mission is to help Master Chief and the Weapon learn from her own mistakes, and become a stronger team. She then disappears, leaving Chief with the Weapon. This represents what is likely the true end of the Cortana plot that has been prevalent since Halo 4, marking a new beginning for the series that will move forward with this new AI, the Weapon, as Master Chief's primary companion.
After escaping the Silent Auditorium, Master Chief and Cortana reappear on the surface of Zeta Halo, where the Weapon explains that multiple days have passed on Zeta Halo since they entered the Silent Auditorium. The Weapon explains that the Banished and the Harbinger were looking for something they weren't able to find, which is almost certainly the Endless. Then, the Pilot swoops down and picks up Master Chief and the Weapon.
Then, we get back to Master Chief and the Weapon back on the Pelican with the pilot, who has only been known up to this point as Echo 216. He finally reveals his name: Fernando Esparza. This leads the Weapon into choosing her own name. She says she has one in mind, as long as it's okay with Master Chief. After he gives approval, saying the Weapon gets to choose her own name, the Weapon appears to settle on a choice. While it's not explicitly said, it seems safe to assume that the Weapon chose to call herself Cortana.
Halo Infinite Postcredits Scene
After the credits roll, there's one more cutscene to watch. It's shown to us from the perspective of an unknown character, who gets to a terminal and unlocks a door that leads to a library filled with what appear to be Forerunner artifacts. After the door opens, the orange symbols on the floating tablets begin to glow. This may be the imprisoned Endless being set free, as the Harbinger alluded to in the final speech. The character who opened the terminal is revealed to be Atriox, the Brute who defeated Master Chief at the very start of the game.
