J.R.R. Tolkien> The Silmarillion
But Melian said: "Truly for these causes they came; but for others also. Beware the sons of Fëanor! The shadow of the wrath of the Valar lies upon them; and they have done evil, I perceive, both in Aman and to their own kin. A grief but lulled to sleep lies between the princes of the Noldor."
The Oath of Fëanor was the catalyst of the entire, tragic history of the Elves and even Middle-Earth in general. Fëanor, greatest in mind and body of all the Elves, created three Silmarils, in which was trapped the light of the two trees, Telperion and Laurelin, before they were destroyed by Melkor and Ungoliant. The three great jewels were hallowed by the Valar and were considered the greatest of Fëanor's works. Fëanor swore his oath when the jewels were taken from his stronghold in Formenos by Melkor whilst he was at a festival with the Valar. He swore upon Ilúvatar, Manwë, Varda, and Taniquetil that he would recover his prized creations, lest the Everlasting Darkness destroy him utterly.
What this oath did was more than doom anyone who took it, but also alienated the entire House of Fëanor from the rest of the Elves. Their exile from Valinor; the Kinslaying and burning of the ships at Sirion; and numerous murders, betrayals, and dismal failures after that are all attributed to the Oath. The oath did not only affect those who took it, either. Many, in a lust for a Silmaril inspired by the Oath, doomed themselves to the same fate as the House of Fëanor.
Fëanor's sons Maedhros, Maglor, Amrod, Amras, Curufin, Caranthir, and Celegorm all swore the Oath themselves right after their father. They are the main perpetrators of the Oath after Fëanor's death in the Dagor-nuin-Giliath. All except one quickly met their deaths, and the last of them, Maglor, who was the gentlest and kindest of the seven, was the only one to survive until the Second Age, but by then, he'd done so much evil alongside his brothers in pursuit of the Oath, that when he finally recovered a Silmaril, it burned his hand, as it would have to any other evil-doer. He threw his Silmaril into the Great Sea in despair, losing forever the last one remaining in Arda.