SCP-093 is a red stone disc discovered on the shore of the Red Sea in 1968, classified Euclid for its uncertain behavior in containment. Its engravings are recorded as glowing in different colors according to the degree of regret the bearer carries. Held against a mirror, the disc lets the bearer pass through into another dimension that varies with the color of the glow.
The heart of the horror lies in what is met beyond the dimension. The space on the far side of the mirror is deserted and ruinous, and the exploration logs convey only in fragments that something there has gone wrong. The premise that an inner measure — regret — becomes the key that opens the passage binds guilt and the unknown together.