The stone knife upon Aslan's Table.
The Stone Knife was a famous object, best known for being used by Queen Jadis to sacrifice Aslan on the Stone Table. As its name suggests, the knife had a blade that was made of stone, and was noted to have "a strange and evil" shape.[1]
Jadis also used this knife during the Battle of Beruna to duel with Peter.[2]
After Jadis' defeat, the knife was somehow taken away and placed on Aslan's Table on Ramandu's Island. By then it had become a holy item: When three of the Seven Lost Lords arrived on the island, one of them dared to touch the knife in a fit of anger, which put both he and his companions into a deep slumber.[3]
The knife most likely remained on Ramandu's Island until the destruction of Narnia.