Malcolm Archibald 
The Shining One [EPUB ebook] 

After the campaign against the Norse, Melcorka the Swordswoman is unsettled.
She wishes revenge on Egil the Norseman, yet knows that Defender – her magic sword – cannot kill without cause.
After a visit to the seer Fitheach, Melcorka receives a dire warning. They head toward the Western Isles in search of knowledge, facing many dangers on their path.
With the help of pirate leader Osprey and Hector, leader of the Ulvust, they forge on toward the Standing Stones of Callanish to face the most fearsome foe of all: The Shining One.
This a standalone novel, and can be enjoyed even if you haven’t read other books in the series.