In the summer of 465 of the First Era, Dairon discovered that Luthien had a secret meeting with a human named Beren in the woods of Doriath. He reported this to Thingol, who was outraged and asked Lúthien. Lúthien, however, remained silent until Thingol promised not to harm or ki

In the summer of 465 of the First Era, Dairon discovered that Luthien had a secret meeting with a human named Beren in the forest of Doriath. He reported this to Thingol, who was outraged and asked Lúthien. Lúthien, however, remained silent until Thingol promised not to harm or kill the human. Luthien then introduced Beren to Thingol, and Thingol asked Beren to get a Silmaril as the price for holding hands with Luthien. "The Silmarillion" describes it this way:

Unexpectedly, Beren laughed and said: "It's a joke. I didn't expect the kings of the elves to sell their daughters for artificial jewelry. Thingol, if this is your wish, I will Go and do it. When we meet again, I will hand you the Silmarillion from the Iron Crown; so that you will not underestimate Beren, son of Barahir."

Then he looked at . Melian 's eyes did not say a word; so he said goodbye to Lúthien Tinuviel, bowed to Thingol and Melian, then pushed aside the guards beside him, walked away alone, and left Menegroth.

Due to Dairon's betrayal, Beren left the kingdom of Doriath. He lost the protection of Melian's magic ring and came to the cruel world outside.

Later, Dai Long betrayed Luthien again, and Luthien didn't realize that she was betrayed by Dai Long for the first time. So when Beren was captured by Morgoth, Luthien knew that Beren would be alone and helpless, so after Beren set off, she asked Dairon for help, hoping to follow Beren. However, Dairon once again reported her to Thingol, but this time he was desperate to protect her. In order to restrict Luthien's movements and prevent her from languishing in captivity, Thingol built a hut on the tallest tree in the forest, beech tree Xiliron, and placed Luthien there to guard her. . "The Silmarillion" describes it this way:

At the moment when Sauron put Beren in prison, a great fear fell on Lucy Anxin; after going to ask Melian, she knew that Beren Lun was imprisoned in a dungeon on the island of Mongos, without any hope of rescue. Lúthien could see that no one in the world would help her, so she decided to leave Doriath and find him herself; she went to Daeron for help, but Daeron betrayed her again and gave her to him. The plan was told to Thingol. Thingol was shocked and frightened when he heard the news. He did not want to imprison Luthien in a dark place to prevent her from withering and dying, but he wanted to imprison her, so he ordered people to build a castle on a very tall tree. A hut, so she couldn't escape.

But Lúthien escaped from Cililon and left Doriath. After her escape, Dai Lon fell into remorse. He also left Doriath to seek Lúthien, but he never saw her again. Later he climbed over the mountains to the east of Middle-earth , and lingered by the deep waters there, singing dirges for Lúthien.

His ending is very similar to that of Maglor, who, as the second best musician in Middle-earth, was last seen on the coast in Middle-earth . He wandered sadly. Dai Long was the same, wandering around without a trace.