Book Corner: The Northern Throne by Steven A. McKay

Bellicus the Druid and his friend Duro, a former Roman centurion, have already suffered a great deal in recent years but, for them, things are about to get even worse.
Britain is changing. The Romans have gone and warriors from many different places seek to fill the void the legions left behind. In the south, the Saxons’ expansion seems unstoppable despite the efforts of the warlord Arthur, while north of Hadrian’s Wall various kings and chieftains are always looking to extend their borders.

In Dun Breatann, Bellicus believes the disparate northern tribes must put aside their differences, become allies, and face the Saxon threat together, under one High King.

Or High Queen…

Small-minded men don’t always look at the bigger picture though, and, when Bellicus and Duro seek to form a pact with an old enemy, events take a shocking and terrible turn that will leave the companions changed forever.