Seven Swords

The Seven Swords were swords that were possessed by the Seven Lost Lords that Caspian and the crew of the Dawn Treader voyaged to find in The Voyage of the Dawn Treader. Each sword possessed magical properties, and when all were placed on Aslan's Table at Ramandu's Island, the darkness emanating from Dark Island, which was slowly overtaking the lands of Narnia, would be lifted.

Peter Pevensie's sword, Rhindon, was also shown to have similar magical properties, though it was not one of the seven.

History
According to legend, the swords were created by Aslan during Narnia's Golden Age. He created them to protect Narnia in times of danger.

At some point during the Telmarine Age of Narnia, the Telmarines must have found the swords and held onto them throughout the centuries. Eventually, Caspian IX gave each of these seven swords to his seven most trusted Lords.

After Caspian IX was murdered by his brother Miraz, who then attempted to kill the Lords as well, they fled to the Lone Islands to escape him. While they were there, they learned of the Green Mist that was abducting people, and vowed to find a way to destroy it. Each of them held onto their swords during their journey.

When they arrived at Coriakin's Island, the magician told them that the only way to rid Narnia of the Green Mist was for them to each lay his sword on Aslan's Table. Only then would their true power be released, and Narnia would be saved.

They each set sail, but none of them succeeded. It was only thanks to Caspian X and the crew of the Dawn Treader that their quest was fulfilled.

Fate of the Swords
Lord Bern was a prisoner at Narrowhaven, who hid his sword safely in a cave for years before he was finally liberated by Caspian and his crew, when the island was purged of its slave traders. He then gave his sword to Caspian, who in turn gave it to Edmund.

Lord Restimar was turned into gold on Deathwater Island, but his sword remained unchanged because of its magic. The sword was retrieved by Caspian, Edmund, and Lucy.

Lord Octesian, who was on the same island, died of unknown causes, with his sword, clothing and skeletal corpse remaining amidst a river of gold riches until found by Edmund and Caspian.

Lords Argoz, Mavramorn, and Revilian were put into an enchanted sleep, which they would remain in until the darkness was gone. When they were first found by Caspian and his crew, they found the frozen lords at Aslan's Table with their swords under the weeds. They placed all the swords, except for one, on the table.

Lord Rhoop was a surviving lord that spent some time on Dark Island. Later on, he would be found by Caspian, along with his sword. But in a fit of madness and anxiety, Rhoop flung his sword at a dragon-turned Eustace, who then flew away with it.

After Eustace was changed back into a boy by Aslan, and sent to Ramandu's Island, he took the remaining sword to Aslan's Table, and joined it with the other six, ridding Narnia of its darkness once and for all.