Mary Stewart: Las Colinas Huecas (Paperback, Spanish language, 1996, Ediciones B)
Paperback
Spanish language
Published Nov. 23, 1996 by Ediciones B.
Dark Ages. Keeping watch over the young Arthur Pendragon, the prince and prophet Merlin Ambrosius is haunted by dreams of the magical sword Caliburn, which has been hidden for centuries. When Uther Pendragon is killed in battle, the time of destiny is at hand, and Arthur must claim the fabled sword to become the true High King of Britain.
See comment on The Crystal Cave. This trilogy should be read all at once. It's not very long.
