The official GemStone IV encyclopedia.
Twisted and warped in the service of the Council of Twelve, the apprentice floats several inches over the floor, hunched over, gazing at his surroundings with abnormally large yellow-hued eyes framed by translucent, rotting and pestilent skin. Draped over his broken form are the remnants of a once simple, but finely crafted robe. Cinching the robe at the waist is a thick black belt, adorned with numerous leather pouches once used to hold the supplies desired by his arcane master.
Ethereal mage apprentices are noncorporeal, so they cannot be stunned and and will not receive critical injuries. Spells or maneuvers which can induce roundtime are effective at preventing them from casting their spells if those are a concern, however any of the other denizens of the Citadel that happen to also be in the room should be a higher priority.