Only four Class-D personnel are seen in-game. One is seen being escorted by two guards during the intro sequence. Two are seen in the opening scene inside SCP-173's containment chamber. When the door control system begins to malfunction one of Class-D's will begin walking towards SCP-173 cautiously, while the other will express concern that something is wrong. Once the lights go out SCP-173 will kill one of the Class-D's, the other will gasp and back up before getting killed as well
The other Class-D is the lure subject used to attract SCP-106 in the recall protocol to re-contain the SCP. The subject would have his femur broken, with his screams broadcasted over the intercom system, luring SCP-106 to re-containment
In addition there was also another Class-D used as a lure subject to contain SCP-106 in its breach prior to the events of the game, under the designation D-9215