From Halopedia, the Halo wiki
By 2555, Carl Radeen served as an aide for Captain Annabelle Richards, the head of UNSC Special Forces, who served under the Office of Naval Intelligence's administration. In 2555, after it was discovered that the Halo Array's firing sequence had been activated on a five-week countdown, UNSC administration decided that a joint UNSC–Swords of Sanghelios team needed to be sent to Installation 00 and attempt to stop the sequence. Richards, along with Radeen, oversaw attempts to reactivate the slipspace portal to the Ark at Voi, Kenya on Earth. When the Sangheili arrived at the site, Radeen warned Richards of Spartan Frank Kodiak's disdain for the species, but she dismissed his claim.
After the portal was activated, a Retriever exited and began mining Earth's surface. After the Sentinel was destroyed, Radeen and Richards met aboard the Sangheili corvette Mayhem with the rest of the team to discuss the current situation. After the corvette continued through the portal and crash-landed on Installation 00, Radeen remained behind on Mayhem with most of the UNSC Marines to secure the vessel and help the Sangheili repair the ship, if needed. After Richards injured her leg and returned to Mayhem with the rest of the surviving Marines, she received treatment from Sehar. When monitor 000 Tragic Solitude unleashed an army of Retrievers through the portal to mine Earth, Radeen informed Richards after her surgery and the two watched the Retrievers enter the portal from the ship's bridge. Eventually, the rest of the team stopped the monitor and averted the activation sequence, and the crew of Mayhem returned to Earth.
Personality and traits
Radeen is noted to be tall and burly. Captain Annabelle Richards once compared him to an android, as he never smiles, laughs, frowns, or expresses any sort of reaction to any event. Radeen never looked Richards in the eye while speaking to her and instead focused on the space just to the right of her shoulder. Richards believed that this was due to some deeply ingrained concern over respect. Radeen rarely questioned the orders of his superiors and was known for completing his tasks with customary swiftness.
List of appearances