Dairuin was a servant of the house of Barahir in Dorthonion. After Dagor Bragollach he continued resistance against Morgoth's forces under Barahir's command. At last Barahir had only twelve men of which Dairuin was one. He was killed in 460 First Age, when Sauron attacked Barahir's camp after Gorlim had deceived them. Only Beren, son of Barahir, survived being out of camp during the final attack.