What are the Twelve Treasures of Britain in the book, The Winter King: A Novel of Arthur?

Twelve common, ordinary objects given by the Gods to British tribes but lost and dispersed in Roman times, the treasures are, in the Druid Merlin's mind, the key to regaining Britain's religion and legacy. He spends his life finding them and the only written Druid document, penned for the Romans by the captive Druid Caleddin. Missing for two-thirds of the novel, Merlin finds the scroll in Normandy and then disappears in further searches. He reappears at the great Battle of Lugg Vale, declaring that the Britons must drop everything, unite, and find the thirteenth and greatest treasure, the Cauldron of Clyddno Eiddyn. When all of the objects are brought together, the Gods will return and hear Britons' prayers.