Later, he became a good friend and brother-in-arms of Túrin Turambar. When Túrin left Doriath, Beleg got permission from Thingol to follow him into exile and bring him the kings pardon, wielding the black swordAnglachel that Eöl had forged and given to Thingol in tribute. Beleg found the band of outlaws Turin was leading while Turin was away scouting, and was tortured by the outlaws until Turin found and released him. Unable to persuade Turin to return to Doriath with him, Beleg returned to King Thingol and gained permission to join Turin. He went into the wilds again and found Turin on Amon Rûdh. Together with Túrin, wearing the Dragon-helm of Dor-lómin, he became for a while a captain against Morgoth, and the land they dwelt in became known as the Land of Bow and Helm or Dor-Cuarthol in Sindarin.
When Túrin was captured by the Orcs, Beleg was grievously wounded, yet with the knowledge and strength of an elite elven warrior, he recovered and followed the Orcs. He met the escaped thrall Gwindor in Taur-nu-Fuin and together they rescued Túrin, but as Beleg cut the bonds from Túrin's wrists and ankles he slipped, accidentally cutting Túrin with his sword. Túrin awoke and did not recognize Beleg in the darkness, assuming the shape bent over him with a blade was an orc and that he was to be tortured again. In a sudden rage of self-defense, he wrested the sword from Beleg and killed him.
After his death Túrin made the song Laer Cú Beleg, The Song of the Great Bow, and was known to sing it at times of grief and pain, in honor of his fallen friend and comrade.
In early writings, Beleg was not immediately killed by Túrin. After an ambush, Túrin was taken alive and Beleg was left for dead. He was eventually healed of his wounds by Melian, which allowed him to continue in search for his friend. He came upon Gwindor in Taur-nu-Fuin, and together they rescued Túrin. However, Túrin slew Beleg by misadventure.