in the tale of the nauglafring the coming of the dwarves from nogrod is only known when they approach the bridge before tinwelint 's caves ( p. 226 ) ; on the other hand , it is said ( p. 230 ) that the 'woven magic ' of the queen was a defence against 'men of hostile heart ' , who could never make their way through the woods unless aided by treachery from within .