As with the other Sons of Fëanor, Maglor was bound by an oath to recover his father's Silmarils, which had been stolen by the Dark Lord Morgoth. This oath took the seven brothers to Middle-earth during the First Age where they established realms in exile, waged war against the armies of Morgoth, fought their own Elvish kind, and eventually brought ruin upon themselves.
Hearing that a surviving Silmaril was in the possession of Elwing, the wife of Eärendil, he and his brother Maedhros, through reluctant for a time mounted an attack on the Havens of Sirion with their remaining followers. Although they won the fight spilling much of their kin's blood, they did not get the Silmaril as Elwing escaped over the Great Sea with it. After the carnage of the cruel bloodletting, he and his brother came upon the two young sons of Eärendil and Elwing, Elrond and Elros. With so much blood already on his hands Maglor took pity on them and would not allow them to be slain. So in the absence of their parents he took them into his household and raised them as if they were his very own children.
After the War of Wrath, he and his last surviving brother, Maedhros stole the two remaining Silmarils taken by the Valar from Morgoth, even though initially Maglor tried to dissuade his older brother from doing this. But because of the evil deeds committed by the brothers to regain the jewels, they burned in Maglor and Maedhros's hands. Unable to bear the suffering, Maglor cast his Silmaril into the sea. Thereafter he wandered along the shores of the world, singing laments over the loss of the jewel, until he faded from memory.
Tolkien refers to Maglor as one of Fëanor's sons that were probably married, but we have no information on his wife or any children of his own.
Speculations on FateEdit
Maglor was described as simply wandering off at the end of the Quenta Silmarillion not dying by committing suicide, like his older brother or by anything else. Of course with all of Beleriand falling into ruin and chaos, he could have been caught in the vast destruction of the area and killed but this was never really documented. In the event that he was killed, it would likely have been documented. There is a legend saying that he still lives wandering the coasts of Middle-earth still singing lamentations of pain, regret and despair, either as a corporeal being or a spirit forbidden to return to Valinor until the end of time.
Maglor is a Sindarin rendering of his Quenya mother name Macalaurë, which means "Gold-cleaver" — possibly alluding to the power of his voice. (He was also known as "Strong-voiced".) The meaning behind Maglor's father name, Canafinwë, is uncertain, but probably contains the prefix kana/o (commanding) + Finwë.
The House of FëanorEdit
Finwë = Míriel Mahtan | | Fëanor = Nerdanel | ------------------------------------------------------ | | | | | | | Maedhros Maglor Celegorm Caranthir Curufin Amrod Amras | Celebrimbor