In Amber Clad

The UNSC In Amber Clad was a warship commanded by Miranda Keyes that took part in the fight against Big Fluffy Monkey Man and his minions. The ship landed on Halo Installation 05 after the First Battle of Earth in the Human-Covenant War and attacked the Library there. After the death of the Prophet of Regret at the hands of Johnny, the ship was overtaken by the Flood and invaded High Charity, slipping inside the giant city and crashing into one of the towers there. From the wreck of the frigate thousands of Flood Forms and the newly awakened Gravemind attacked High Charity, distributing themselves via Pelicans Dropships.

The wreck of the In Amber Clad was going to be used by Cortana as a means of destroying High Charity but the ship was too heavily damaged to establish a link to its central computer. Why Cortana didn't simply blow the ship up herself, we will never know. When High Charity crashed on the Ark, many of the towers inside the city collapsed and the In Amber Clad was likely obliterated when this happened. If not, it was certainly destroyed when Johnny flew into the city, saved Cortana and blew the place up.

Jenkins served on this ship and witnessed it crash, as he happened to be inside High Charity with Johnny when it slipped in. Many believe that it was the ship slipping in that momentarily distracted Jenkins, allowing a Jackal Sniper to pick him off.