There are 3 books in the The Sun Wolf and Starhawk series. The newest book is The Dark Hand of Magic which came out in 1990.

1
The Ladies of Mandrigyn

Book cover of The Ladies of Mandrigyn
First in the series from a New York Times–bestselling author and “fabulously talented writer” featuring a brilliant mercenary and his fierce female partner (Charlaine Harris).
 Gifted with courage, strength, and the intelligence to know when to fight, Sun Wolf is the greatest mercenary in a land overrun by war. With…
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2
The Witches of Wenshar

The Witches of Wenshar
Once, it was said, Wensha had been a city of witches, summoning and controlling demons for their evil magic. But in nearby Tandieras, Kaltha claimed to have found their lost book of spells to perform only white magic. When Sun Wolf arrived, he discovered increasing signs of evil magic and…

3
The Dark Hand of Magic

The Dark Hand of Magic
Sun Wolf knew he had the power of magic, but he needed a master wizard to teach him to fully use his skills. But there was no one who could do the job. When he was called upon to help old friends against the ancient wizard, he did -- thus…