From Halopedia, the Halo wiki
The Command Mantis is a hero vehicle deployed by Commander Jerome. It is an upgraded variant of the Mantis all-environment bipedal walker armed with twin high energy lasers and fitted with an advanced energy shield.
The Mantis can operate in an unmanned combat mode or be piloted by Commander Jerome. When piloted by Commander Jerome the mech's long-range missile launchers are also deployed, though these do have a minimum engagement distance. Jerome-092 is free to disembark at any time with the unload ability.
The Command Mantis is tailored specifically for Jerome's neural interface and cannot be Hijacked. Upgrades to Commander Jerome also affect the Command Mantis, and he continues to Inspire while operating the mech.
Nicknamed Theseus by Jerome-092, his personalized Command Mantis is a mobile command post and linebreaker unit that complements both his augmented physiology and leadership style. It incorporates one of the Spirit of Fire's command—and—control nexus relays, enhancing Jerome's situational awareness of the battlefield and serving as a backup for the UNSC battlenet should the ship be crippled or destroyed.