After their return, Fëanor had led his people up the Firth of Drengist, and then eastward to Lake Mithrim, on whose shore they camped. Morgoth saw an opportunity to wipe out his enemies, and sent a vast army of Orcs to launch a surprise attack on the Noldor. Though the Orcs greatly outnumbered the Elves, and had the advantage of surprise, the Noldor quickly turned the tide and routed their enemy. Many Orcs fled back over the Mountains, where they joined with reinforcing armies, but still they were no match for the Elves. Celegorm and his hunters chased them across Ard-galen and into the Fen of Serech, where they were destroyed.
Though it was a mighty victory for the people of Fëanor, the battle saw the end of Fëanor himself. Filled with wrath, he charged on towards Angband, thinking to utterly defeat Morgoth and retrieve the Silmarils. So he left his armies behind, and with just a few soldiers left to him, he was set upon by Balrogs, and fatally wounded. He died soon after, leaving his seven sons to fulfil the great Oath they had taken with their father.
The Dagor-nuin-Giliath changed the face of Beleriand. Before the battle, Orcs had wandered widely outside the protected realm of Doriath, and besieged the shoreland Havens of the Falas. After the battle, the few that remained of Morgoth's hosts had fled back to their master in the North. Though the ultimate cause of the battle was Morgoth's miscalculation of the power of the Noldor, this was not widely understood. Many of the native Sindar of Beleriand mistakenly thought the returning Noldor had been sent by the Valar to free them from the Orcs. In a dark irony, centuries later the Sindarin kingdom of Doriath would be sacked and destroyed by the very Noldorin princes that they believed to be their saviours.