When the player meets M. Ryden in Resurrection of Evil, he is fixing a Sentry Bot. He calls to the player to come to his position, and states that the Sentry Bots are what has kept him alive, but he has sent them ahead into the tunnels. He further states that the player must progress through Maintenance to reach the Monorail. Before the player moves through Maintenance, Ryden reminds the player that the Sentry Bots are friendly, and to stay close to them for survival.