What sort of creatures do the goblins appear to be?

"big goblins, great ugly-looking goblins"

"It was deep, deep, dark, such as only goblins that have taken to living in the heart of the mountains can see through."

"The goblins were very rough, and pinched unmercifully, and chuckled and laughed in their horrible stony voices;..."

"For goblins eat horses and ponies and donkeys (and other much more dreadful things), and they are always hungry."

and most importantly;

"Now goblins are cruel, wicked, and bad-hearted."