Fear the Draugr: Book 2 of The Lost Hunt Series

In the late 8th century 250 years since evil was vanquished in the battle of Londinium, the England-to-be is a group of squabbling kingdoms, their undefended coastlines too tempting to the Norsemen.

A conflicted former monk and a deeply pious fisherwoman released from slavery join forces with a Saxon king in exile eager to claim his throne, a Saracen noblewoman hostage desperate to escape captivity, and a Celtic demon hunter fulfilling his life's work to fight the new menace carried under the decks of the Norse longboats.

Corpses that can walk, corpses with superhuman strength, and corpses that can turn others into monstrosities like them.
The dead walk. Their name is Draugr.