§ Of Beren and Lúthien The Silmarillion

But in the north of his realm his messengers met with a peril sudden and unlooked for: the onslaught of Carcharoth, the Wolf of Angband. In his madness he had run ravening from the north, and passing at length over Taur-nu-Fuin upon its eastern side he came down from the sources of Esgalduin like a destroying fire. Nothing hindered him, and the might of Melian upon the borders of the land stayed him not; for fate drove him, and the power of the Silmaril that he bore to his torment. Thus he burst into the inviolate woods of Doriath, and all fled away in fear. Alone of the messengers Mablung, chief captain of the King, escaped, and he brought the dread tidings to Thingol.