The robot "security" system left holding the abandoned Reaver castle, and the patrol Samantha is dodging.
Samantha reported that the The Reaver Castle was abandoned except for a "security" system — a bunch of robots. She had located Louis in a secured jail cell inside and was waiting for a patrol to move away before attempting to get him out. With Warlord Fang confirmed to be inside The Ball of Flesh, the robots are effectively all that remains defending the Reavers' seat.
Patrolling robots left running in an otherwise empty castle.
The automated garrison of an abandoned castle, and the only obstacle to Louis's rescue.