§ Of Maeglin The Silmarillion

Then Aredhel turned back and sought the dangerous road between the haunted valleys of Ered Gorgoroth and the north fences of Doriath; and as they drew near to the evil region of Nan Dungortheb the riders became enmeshed in shadows, and Aredhel strayed from her companions and was lost. They sought long for her in vain, fearing that she had been ensnared, or had drunk from the poisoned streams of that land; but the fell creatures of Ungoliant that dwelt in the ravines were aroused and pursued them, and they hardly escaped with their lives. When at last they returned and their tale was told there was great sorrow in Gondolin; and Turgon sat long alone, enduring grief and anger in silence.