Gryphon in Glory by Andre Norton is currently free on Amazon (Amazon US, Amazon ES). This is the product description:
Book six of the Witch World - High Hallack Series.
The Waste was stirring and strange forms of the Dark, long quiet, began to wake as Kerovan - whose cloven hoofs marked his kinship with the Old Ones - Journeyed into the Waste on a secret mission, Leaving behind the girl he loved Joisan, however, rode after him, wearing about her neck Kerovan’s gift, a small crystal globe encasing a miniature gryphon. While Kervan strove for answers to the riddles of the Dark, Joisan worked to unlock the power of the crystal gryphon. But only together could they hope to find the ancient Sleeper and defeat the forces of evil.
Some of the ebooks by Andre Norton that were part of the promotion yesterday are still free, so run and grab them while you can.