In Assassin's Creed Valhalla, Eivor's settlement is located in Mercia.
Eivor's Ravensthorpe settlement is established in England after the Viking group leaves Norway. It lies in the region of Mercia, one of the Anglo-Saxon kingdoms competing for power in the game's ninth-century setting. From Ravensthorpe, Eivor builds alliances and undertakes campaigns across several English territories.
The answer can be confused with Wessex, Northumbria, or East Anglia because all three appear in Valhalla's English world. Wessex is especially important because of King Alfred and the political opposition to the Viking forces. However, Ravensthorpe itself is associated with Mercia, not with the settlement's other campaign destinations.
Valhalla combines historical figures and events with fictional characters and supernatural elements. Eivor is a Viking raider who becomes connected to the Hidden Ones through Basim and Hytham. The settlement provides the game's persistent home base, expanding as Eivor gains resources and allies.