From Halopedia, the Halo wiki
Halo Wars 2
Pavium is exclusive to himself and can be built at the War Council. Like other hero units the player is limited to one on the field at a time. Pavium performs well against vehicles, but only okay against infantry, aircraft, and structures. Once the Designator Shell upgrade is purchased Pavium will perform well against infantry and structures. In Blitz he costs 205 energy.