So… this is not very good.
It's a thing that does a thing, and the thing it does isn't very interesting, as we've seen variations of this concept hundreds of times (Terminator, Mystique, and that thing in the wardrobe in Harry Potter, just to name a few).
I took a glance at your sandbox, and unfortunately it doesn't get any better. You classified it as Keter, but making something more dangerous doesn't inherently make it more interesting. Also, is this thing's containment in another dimension? Did I read that right?
You describe this as a solvent, but it doesn't appear to have any properties of a solvent. It just sounds like it's a blue slime from countless RPGs that can transform into whatever it sees. How does it even see without eyes? There's so much lazy expunges throughout that it makes it hard to read, and leads me to believe as a reader that you don't know what's behind those. The Foundation lost what it was they feed this thing? It became sentient due to captivity? All these things add up and cause me to lose my suspension of disbelief. Also, the testing addenda don't add anything to the article, and I don't buy that they're just throwing D-Class at this thing so it can kill them.
