UNSC Apocalypso
From Halopedia, the Halo wiki
The Apocalypso was a United Nations Space Command Office of Naval Intelligence Prowler grom I Love Bees and Dead or Alive 4 backstories. While in Covenant space, the Apocalypso intercepted Covenant transmissions detailing attacks on Troy and Harmony. The Covenant, suspecting that their transmissions were intercepted, sent out a Trojan Horse AI buried in a transmission that the Apocalypso was meant to receive. The AI, calling itself the Seeker, began to subtly corrupt the shipboard AI, Melissa.
Realizing that there was something wrong with her AI, Captain Greene decided to bring the ship back to Earth. Just as the ship was about to head back, long-range scanners picked up a curious object floating in space. The ship's crew believed that the object was a Covenant artifact of new design, but infact it was a Forerunner artifact.
The Seeker attempted to alert the Covenant of the artifact's existence, but without the Apocalypso taking notice. Melissa influenced a crewmember to fiddle with the Forerunner artifact. The artifact sent out an explosion through Slipspace, causing the ship to crash within Lunar orbit and blackouting communications in the Solar System for about* seven seconds.
