Robert E. Howard created the character Cormac Mac Art. The author Andrew J. Offutt continued the adventures of Cormac by writing his own stories. As far as I know, he wrote 6 novels about Howard’s hero.

This is the Zebra book from 1976. Cormac Mac Art, the son of an Irish king, forced to live the life of an outlaw after he is unjustly accused of a crime, is finally vindicated and then pursued by an evil wizard who has waited centuries to seek revenge

Contents

• The Undying Wizard • [Cormac Mac Art • 3] • novel by Andrew J. Offutt

Notes

Stated 1st printing
According to a user on isfdb.com, Locus #196, says the book was published in October but states August.