A mighty bow, made of black yew-wood, that was carried by the most famous archer in Tolkien's tales, Beleg Strongbow of Doriath (in fact his surname, 'Strongbow', is a reference to Belthronding). With it, he long defended the borders of King Thingol, and when he left Doriath in search of his friend Túrin, he took his famous bow with him. Beleg found Túrin dwelling in the halls of Mîm in Amon Rûdh, and together they founded the kingdom of Dor-Cúarthol - the Land of Bow and Helm - with the 'Bow' of that name being Belthronding.
Dor-Cúarthol was a short-lived realm: its leaders were betrayed to the Orcs, and Beleg was left for dead while Túrin was taken captive. Recovering, Beleg set out into the north to rescue his friend. He succeeded, but in a tragic turn of fate Túrin mistook him for a foe, and slew him. Overcome with grief, Túrin dug a grave for Beleg's body, and he buried Belthronding the famous bow beside its late master.