From Halopedia, the Halo wiki
The UNSC Marine Corps of Engineers is a command of the UNSC Marine Corps, conducting engineering operations for the branch. Their tasks include the protection and if necessary, demolition of classified research sites.
One of the units of the UNSC Marine Corps of Engineers is the Hades Corps, which was tasked with the demolition of Office of Naval Intelligence Materials Group's Weapons Research Facility T12A on Algolis at some point during the Human-Covenant War to prevent it from falling into Covenant control. Due to the efforts of Sergeant "Ghost" of Hades Corps, the unit was successful in destroying the facility and its HRUNTING/YGGDRASIL Mark I ADS prototype.
List of appearances