I just killed this mob at 150, 450 on the first floor.
From zone-in, go straight under the ramp. At the T...make a right...there is a little cul-de-sac room with 3 shissar in it at the end of this hallway. Magister spawned in the middle.
You can invis all the way there, but the three shissar in this room see invis. Mob was a pushover for me (level 65 enc) and my gimpy pet.
EDIT: This mob can be slowed. He just has slightly higher than average MR (resisted Insanity twice and my first slow...pretty high for a level 53 mob).
Since both 1st and 2nd floor commanders can spawn in all kinds of different places, they dont really a good reference point. Does anyone know where this mob spawns?
Was with a group the other night just clearing mobs to get comm1 to pop. This seemed to be a random named on the first floor, not far awaw from the main hallway. Dropped the boots and the book. Couldn't be slowed, could be crippled. Not as hard as a an elite guard. Spent most of his time casting spells that were interupted, or resisted.