But that's not how the classification system works.
It's danger and power is irrelevant, but how difficult it is to keep locked away.
If you can set it in a box and leave it there, it's Safe.
If you can set it in a box and it leaves, but all you have to do is set up some mundane shit like a strong lock, it's Euclid, as in Euclidean, as in the geometry of normal experience.
If you set it in a box and it leaves, so you have to set up some elaborate bullshit to convince it to stay, it's Keter, as in the topmost sephirot of the Tree of Life, as in wacky bullshit is going on.
If it IS the box, it's Thaumiel.
And then there's a handful of very specific classifications.
My favorite example is SCP 1425- Star Signals, Class Safe.
It's a normal book by any means and it's containment is just a simple locker. But the shit it teaches can lead to an XK End of the World Scenario.
Safe does not mean Safe.