Unknown beings!?

[Lalwendë]

Also Gandalf mentions there being strange creatures gnawing at the root of the mountain. Gnawing is a direct reference by Tolkien to Níðhöggr.

Ulvenok, you've picked up on one of my favourite things there. I like digging out these references in Tolkien's work and he couldn't have chosen anything more frightening to be lurking under the Mountains (especially if you read the stark way the Niddhogr is described in the Voluspa).

I think the very presence of characters like Tom and Goldberry, and the 'nameless things' (and Pukel Men, and Ents etc) hints that there were more creatures and being in Middle-earth than we meet in the stories. That 'layering' adds the depth to Tolkien's creation that is missing from a lot of other stories. I'm not sure if Tolkien intended that, but it works in any case.

As to 'power' I think it can't be doubted that Ungoliant had an incredible level of it. Have a nose around because there's quite a lot of things on here about this subject.