33RRR THIRD GUARDIAN. The wall with the door, the floor, and the ceiling are made of a dull gray material, while the other three walls are made of a metal so shiny as to act as a mirror. The room is very cold, but will do no harm in the short term.
In the center of the room is a green transparent humanoid with a thick crocodilian tail and a head like that of a shark. The three reflective walls mirror the shape of this creature, but not of the adventurers.
Third Guardian (AC 2; MV 0"; HD 9; hp 40; #AT 0; D Nil; SA Breath weapon; SD See below; XP 1780)
The third guardian's central body cannot attack, but if it is attacked it will only take 1 point of damage. The reflections can attack by breathing a cone of frost which can reach any part of the room, doing 2d8 damage (save for half). These reflections can be struck and take half normal damage from all attacks except for cold, which the guardian is immune to. The guardian is not affected by mind-affecting spells.
Defeating the guardian causes the central body to turn into a green crystal key. The green key, along with the black and red keys, can be used to open the door to Room 33SSS.