The Seer of Serone by James Priest

This is a novel, The Seer of Serone, by James Priest, telling of tiny magical beings dwelling the world over. They are kirins. It is a quiet summer's day in the domain of Yorl and Moger kirins, tree-dwellers in the central part of North America. Speckarin is magician to the Yorls, living on Rogalinon, a towering and majestic oak. But this story opens far from that idyllic setting, at Stonehenge, the hanging stones, the citadel of kirin magic. There Fairmean, a depraved magician, commits an act of pure and unadulterated vengeance, imperiling every kirin on Earth.