From Halopedia, the Halo wiki
UNSC Toulouse was a Halcyon-class light cruiser in service with the UNSC Navy. Unlike her sister ship UNSC Pillar of Autumn, Toulouse was not upgraded with improved engines, weapons, and a smart AI. During the Human-Covenant War, Toulouse engaged several CCS-class battlecruisers over an unidentified Forerunner installation that was not a Halo ring or an Ark. Severely outnumbered and outgunned, Toulouse was likely destroyed in this engagement.
UNSC Toulouse is featured in the cover art of Halo: Warfleet, illustrated by Nicolas Bouvier. The cover art depicts Toulouse engaging CCS-class battlecruisers over "a strange – yet somehow familiar – alien installation."