The moon worshippers

Enhanced descriptions from Syndetics:

I shall tell you how a young Negusi warrior made it possible for us to defeat Charlemagne, and the part he played against the Sisters of the Moon...'These are the dying words uttered by a Basque warrior, poisoned and dumped at the doorway to a Benedictine Monastery high in the Pyrenees. The frightened monks understand from these words that the warrior has deep knowledge of one of their closest secrets... The deathbed confession of the warrior continues in a series of flashbacks as he reveals more about the mountain ambush the Basque tribes set for Charlemagne, King of the Franks, as he returned from an unsuccessful invasion of Spain. The monks learn of the power of the Negusi - and of the heroism of a young Basque boy and his wolf dog, without whom the defeat of Charlemagne would have not been possible. This historical adventure story for young adults brings the 7th century vividly to life and captures both the spirit of the Basque people and the history behind the rule of the Emperor Charlemagne, one of the greatest military leaders of the Middle Ages.