It is a large lizard-like creature with enormous teeth and claws who inhabits a SHU cell. The creature has an extreme sensitivity to light which is why there's tinted glass shielding the lamps in its' cell and is also extremely vicious. In "Sanctuary for All", John Druitt kidnaps Ashley and imprisons her in the creature's cell in an attempt to force Magnus to give him a vile of her blood which he needed to pro-long his life. Will was able to break the tinted glass covering the lamps in the creature's cell forcing it to retreat long enough to save Ashley before it ripped her to pieces.