The Battle Edit
By the morning of September 22, the majority of the Covenant ships abandoned Alpha Halo, evident in so few remaining in the vicinity of the debris field. One of these ships included that of the Supreme Commander, Thel 'Vadamee. The remaining seven ships under the command of the Ascendant Justice, which served as a task force for the Second Fleet of Homogeneous Clarity, searched the area.
Unbeknown to the Covenant, John-117 and several other UNSC personnel escaped before the destruction of Installation 04. John, on board a Longsword interceptor and with the aid of Cortana, managed to locate the Cryo-chamber of Linda-058, that was jettisoned out of the UNSC Pillar of Autumn before it crashed. Soon, another signal was detected from a UNSC Pelican dropship, hiding behind a piece of debris from Installation 04. Unfortunately, the Covenant soon spotted the humans. Cortana manoeuvred the ship into a slingshot orbit around Basis, Threshold's moon, and while on the moon's far side, they picked up the survivors from the Pelican. The survivors abandoned the Pelican, loaded it with multiple Moray space mines and sent it ahead of them as they prepared to hijack the Ascendant Justice, the flagship of the Covenant fleet. Coming around Basis, they faced multiple Seraph fighters, but managed to destroy them with Moray mines.
Piloted by Shiela Polaski, the Longsword managed fly into the flagship's hangar. From there, the humans made their way to the bridge, where John dueled a Sangheili warrior, barely winning the duel. Soon, Cortana vented the atmosphere out of the rest of the ship, killing most Covenant aboard.
As the ship was now captured by the UNSC, the other Covenant ships started to fire on it. The Covenant AI in the ship's systems also blocked Cortana's access to the ship's navigation controls and the Slipspace drive, preventing them from escaping. During the engagement, Cortana maneuvered the ship deep into the gravity well of Threshold, and the other Covenant ships followed. Meanwhile, John-117 took a Huragok to fix the ship's power coupling that kept Cortana from accessing the Slipspace drive. At the last moment, the creature managed to fix the coupling, and while Cortana had thought a Slipspace jump, as deep into the atmosphere as they were, would be impossible, she soon realized the extent of Covenant Slipspace technology and managed to perform an in-atmosphere Slipspace jump away from Threshold.