This is the last named mob on this floor so you need to kill all of the other named mobs to reach him
Pick up A Summons from the table located at 62.00, 209.00, 5.00
Strategy
Sergeant Schriber does not aggro until you engage him so position your group in front of him and your tank behind him in the corner.
When you are ready have your tank pull him. (This mob is tank and spank so burn him.
A few seconds after you pull him mobs with very few hit points will spawn around the corners of the room. They will start slowly walking towards Sergeant Schriber. Each mob that reaches him will heal him for 10%.
You will need to either mezz the adds, kill them kite them or dps them to prevent them from reaching the Sergeant.