Forerunner Despair-class fighters saw action during the Forerunner-Flood war against the rogue Monitor Mendicant Bias. After the firing of the Halo superweapon, some of these fighters moved to Shield Worlds and Halo installations.
The Forerunner ship found and reactivated by Colony's Huragoks was 'regrown' from a ship-seed planted by the Librarian prior to the Halo activation. Ship-seed technology provides all the building blueprints needed to built a ship upon activation using on-site materials.