The Beast Hunt in Anghabar was a plot event early in the game, following on from the mine collapse.
Survivors of the mine collapse reported the presence of a red-eyed beast that attacked Tuor. A hunting expedition was arranged to slay the beast, and it was discovered to be a type of komodo dragon, used as raw material in the creation of Glaurung. The creatures had retreated to the mines and formed a colony there, living quietly until disturbed by mining Elves.
The fell beasts were fierce fighters, capable of claw attacks and acid breath/saliva.