Ferum
Some kind of nesting creature.
Appeared from somewhere unknown pre-Spellplague. They possess the ability to reshape their flesh, and have a magic reflection/nullification aura. They seemed to follow magical traces, possibly to consume the magic. This proved to be very bad for the local magocracies as the Ferum decimated their civilization.
Ferum would sometimes eat the skin off people. Mostly they appeared as hairless humanoids, although they took traits from whatever skins they had consumed. There is an implication they had some control over this affect. Their bodies would dissolve upon death. They were immune to fear, and were said to not feel pain. Not much was known
Post-spellplague the gods secreted them away to a chamber at the very bottom of Carceri, held at bay by the Staff of Mystra. Over the centuries they've died or eaten each other until only two remain.
