The raid of the Orc-captain Boldog into Doriath, seeking to capture Lúthien for Morgoth, was an important element in the history of this time, though later it disappeared and there is no trace of it in The Silmarillion. Discussion of it is postponed till later in the Lay of Leithian, but it may be noticed here that an early reference to it is found in The Children of Hurin (p. 16 lines 392 - 4, p. 117 lines 764-6). There it was Thû himself who was bidden by Morgoth go ravage the realm  of the robber Thingol.
Tolkien, Christopher, ed. The History of Middle-Earth III: The Lays of Beleriand. (London: HarperCollins, 2002.) 235 (The Lay of Leithian, Commentary on Canto VII)














