The oath commanded Fëanor to press to Middle-earth and resulted in the first Kinslaying at the havens of the Teleri. Fëanor died soon after his return to Middle-earth but the remaining oath-takers, his sons, lived on in relative harmony with the Eldar of Beleriand. For the greater part of the First Age the oath kept the sons of Fëanor united in one cause to defeat Morgoth and retrieve the jewels.