Euclid

An SCP object is classified as Euclid when its behavior cannot be unerringly predicted, either because the item is sentient, it behaves outside of current scientific knowledge, or its nature is simply poorly understood at present. Euclid-class objects do not pose the same existential threat to humanity due to containment breach that Keter-class objects do, but they still generally require more diligence to keep contained than Safe-class objects.

SCP-008

SCP-1123

SCP-042