I entered a room and there were 2 controllers, each "controlling" these gladiators. When you enter the room a message says something like, "please be quiet and still, the controllers need to concentrate on manipulating these mighty beasts. If they falter they may break loose and wreak havoc on us all!" So im guessing the controllers are chanters and have charmed the gladiators? Anyways the 2 gladiators in the room were battling eachother, although neither was doing any damage. Was just kinda cool to see. btw, they are HUGE! On the pic above a human will only come up to its knee.
Faction hits on these guys are negative to Nihil, so I don't advise killing them. Incidentily they didn't seem anymore difficult than the bats/rats really.