Describe symbolism in The Other Wind by Ursula K. Le Guin

The Lebannen's Stone is what King Lebannen has about his neck in a small drawstring bag at all times a black pebble taken from the mountains of Pain that edge the Land of the Dead. It is both a symbol and a reminder reminder of his fateful journey there, which was recounted in a previous book with Ged called the Archmage of Earthsea.