Encounter Key: Middle Dungeons Level 4.

This level is located seventy feet below Sub-Level 3A. This level directly connects to Levels 3A and 5, and also connects to the Yawning Stairway, with access to multiple other levels.

Except where noted otherwise, the walls and floor are white tile. The ceilings are made of white panels that radiate light equivalent to modern light bulbs. Ceiling panels or their fragments will continue to radiate light for a week, even if removed and carried around by adventurers to other levels. Many of the doors on the level are actually hatches, made of metal and having a central wheel, like on board a submarine. These can be closed to hermetically seal off a part of the level, designed as a measure to limit the spread of dangerous substances accidentally released.

Level 4 was once a research facility, staffed by human researchers under the direction of Doctor Valerian Triskelion. The researchers were involved in many sinister science-fiction type projects, including developing new plagues, cloning people and dinosaurs, and magic robotics. Their principal focus, however, was on the creation of vat creatures in various vat chambers located throughout the level. Genetic information, which the researchers called 'essence', was gathered using essence extractors or huge syringes. Valerian developed an gray organic fluid called vat media which served as the base material for vat creatures and was also used to make food for the creatures in manna machines scattered about the level. Valerian was responsible for the cellar dwellers found in Inner ward The Cellars and he influenced Pelleas Triskelion, who developed his own vat creatures in the Inner Ward Level 3.

However, the most common vat creatures were vat men whose appearance mirrors the Triskelion statues, thus there are laughing, scowling, and crying Triskelion vat creatures, all at war with each other. Vat men are intelligent and can speak, but have bizarre emotions and motives based on modifications performed by researchers on their brain chemistry. A fourth type of vat man, the blank faced Triskelions exist to serve as janitors and repair staff. Vat men all look basically alike. They are man-sized and wear the same white hats and clothing, but their faces serve to set them apart.

Laughing Triskelions: The laughing Triskelions are under the impression that they must eradicate the scowling and crying Triskelions for their own good. They regard this mission as an act of benevolence.

Scowling Triskelions: The scowling Triskelions desire to enslave the crying Triskelions because they enjoy causing hopelessness and suffering. The regard the laughing Triskelions as no real threat and ignore them unless a confrontation is forced upon them.

Crying Triskelions: This group seeks to eat the laughing Triskelions, as they believe that doing so will cure them of their melancholy. They flee from the warlike scowling Triskelions, unless they outnumber them by odds of greater than 2 to 1.

Blank-Faced Triskelions: These vat men have their own mini-complex hidden behind a secret door (Rooms 72 to 79). They will never attack unless forced to defend themselves. They perform cleaning and repair duties that are beyond the scope of the vat spawned gelatinous cubes from Room 45.