From Halopedia, the Halo wiki
Certain Brutes captured by Yapyap are given an Unggoy master to ride them into battle. Some Jiralhanae are awarded specialised plasma gauntlets to help their fists deal more damaging strikes on enemy equipment and personnel.
The Plasma Gloves appears in the PVP multiplayer mode of Halo Wars 2. The weapon is wielded by the Brute Rider units with a Grunt in command. They can also be used in Blitz by the Grunt Riders unit, exclusive to Yapyap players.
List of appearances