Fen of Serech
The Fen of Serech lay on the upper course of the mighty River Sirion, at the inflowing of its tributary, the Rivil. Lying as it did at the mouth of one of the few passes in the northern mountains of Beleriand, the Fen played a part in many battles, and had a long and bloody history.
This history started at the very beginning of the First Age, in the Dagor-nuin-Giliath, which saw a great victory for the Elves over the forces of Morgoth. As the remnant of the Orc armies fled back from the Falas, Celegorm rode down from the hills around Eithel Sirion and drove them into the waters of Serech.
In 455 (First Age), at the Dagor Bragollach, Finrod Felagund found himself cut off in the Fen with a small host. He seemed lost, but was rescued with great loss by Barahir and escaped back to Nargothrond. This was the beginning of the great friendship between Finrod and the kin of Barahir, and Finrod gave Barahir his ring in token of this.
The Elves' counter-attack, the battle that became the Nirnaeth Arnoediad, was made sixteen years later. King Fingon drew up his battle-line along the upper course of the Sirion, between the Fen and the fortress of Barad Eithel. It was here that the heralds of Morgoth tortured Gelmir before the Elven host, and Gwindor his brother broke ranks, driving into the Orc host seeking his revenge, and starting the great battle.
Later, as the battle drew to a close, Turgon and the host of Gondolin were forced back across the Fen. Húrin and Huor, with the men of the House of Hador made a stand there on the banks of the Rivil, allowing Turgon to escape the ruin of the Elves and reach Gondolin. Huor and his men were slain one by one by the Orcs, but Húrin slayed seventy of the enemy before being captured.
After twenty-eight years of torture, Morgoth released Húrin and set a watch upon him. Húrin's first act was to seek out the hidden city of Gondolin, but Turgon was suspicious and ignored his cries; 'Turgon, Turgon, remember the Fen of Serech'.