Morethanjustabaystate

Alfred:.....

Thaumiel is not a typical object class. Most SCPs are either Safe, Euclid, or Keter. A common misconception is that these describe how dangerous an object is, but that’s not it; object class is based on how easy they are to contain.

For example, a Safe object might be capable of causing apocalyptic damage, but if you put it in a box, it will stay in the box. (Though there are a lot of Safe SCPs that are genuinely harmless as well) 

Put a Euclid object in a box and it will usually sit in the box and not make active attempts to escape, but might escape incidentally, due to inherent unpredictability (for example, many sapient SCPs are classified as Euclid even if they’re normally friendly, just because they have free will) or just because the Foundation doesn’t understand it well enough to give it a true safe containment.

Keter objects will actively try to leave the box, and are typically malicious about it as well. Alternatively, they require so much time and energy to contain that it’s nigh-impossible to effectively contain, or are extremely poorly understood.

Thaumiel is special, because.. it is the box. It’s the object class that the Foundation uses for SCPs that are used to contain other SCPs.