Item #: SCP-688
Object Class: Euclid
Special Containment Procedures: SCP-688 may be kept in any location in which physical interaction can be limited. Currently stored in a plexiglass enclosure, 1.5m x 1.5m x 1.25m. Any proposed interaction with symbols or attempt to damage object must be pre-approved by Level 3 personnel. Video surveillance maintained at all times.
Description: SCP-688 is a 1m cube, mass approximately 78kg. Object appears to be composed of square "white onyx" (cryptocrystalline quartz) tiles (64 per side) of identical size but with non-repeating color band variations. Object was identified as an SCP by Agent ██████ during investigation of ████████ incident due to suspected aberrant structural strength - it was the only object larger than 31cm to survive without severe damage (SCP showed no apparent damage). Object emitted unpredictable levels of internal illumination during and after recovery, but has since stabilized to [DATA EXPUNGED]. Variations in light intensity are contiguous, appearing as shadows of humanoid figures and/or equipment, though not corresponding to any persons or devices present. Observers have occasionally reported seeing symbols on the four central tiles of each face. Symbols have not yet been successfully imaged or identified.
Illumination is not internally-generated, emissions appear to be correlated with exposure of SCP-688 to identical emissions approximately 43.6 days previously. Subsequent testing has verified that all EM radiation incident upon the surface of SCP-688 in the visible range eventually emerges from the opposite face approximately 43.6 days later. No other EM radiation is affected. (See Appendix A for technical details.)
No verifiable record of the damage of SCP-688, or of a sentient touching one of the symbols exists. Interviews with test subjects suggest that such actions are possible, but result in a temporal loop in which the subject maintains awareness but loses the ability to control their actions. These loops vary in size but do not exceed 43.6 days. The subject only escapes from the loop when quantum-level fluctuations cause an actual macroscopic change which prevents the original interaction with the SCP, and thus the number of repetitions of a loop is almost always extremely large. Changes to events which prevent interaction range from innocuous to fatal, (see Log SCP-688-A for details). The psychological effects on a test subject of this degree of repetition almost always include extreme psychosis. Effects are difficult to remove via amnesiac, maximum safe dose is usually not effective. As the effects can be avoided simply by not interacting with 688, classified as Safe.
Addendum 688-1: Experiment Log SCP-688-A
Addendum 688-2: Due to unpredictable side-effects of testing which can expand far beyond the SCP (see experiment log 688-A-4), reclassified as Euclid.