Evil Eyes.
These gelatinous blobs are a very fearsome sight when first viewed, but are rather harmless for the most part. Used as sentries by the Empire, they will only attack delvers when they enter their line of sight. They are most commonly found in large groups in areas surrounded by pits.
What confuses the Guild members the most is how the eyes actually manage to eat their prey. Because of their lack of mouths and known digestive organs, it is still unclear as to how they digest their prey. This does not make them any less deadly, however.
An eye's vision is only blocked by walls, obstacles, and doors. They are able to spot delvers over pits and through mineral based substances such as tar and mud. They don't have any restrictions on the distances they are able to see, so the only safe way to keep a eye asleep is to never enter its line of sight. If you happen to enter it, the evil eye uses the same mentality as the common dungeon roach.
Of course, life could also be much easier for a smitemaster if they were able to leave an eye sleeping.
Detailed Behaviour Analysis
Sleeping evil eyes are stationary.
Their gaze is in a continuous straight line extending from the tile they eye is on in the direction it is facing.
The gaze is blocked by walls, doors and mirrors, but not by monsters or tarstuff. Mirrors will not only block the gaze but will reflect it so that the line will extend behind the eye as well as in front of it.
If the player or a decoy, clone, stalwart or solder walks into this gaze the eye is woken and begins moving the same turn. If the player is invisible and outside of the "smelling range" of the potion, the eye will not be woken. However, decoys will always wake an eye, regardless of whether the player is invisible.
A woken evil eye moves in the same way as a roach.