After a number of successful operations elsewhere, he came to Northumbria and appears at some point to have set himself up as king. King Eadred responded harshly to the northern defectors by launching a destructive raid on Northumbria, which notably included burning the Ripon monastery founded by St. Wilfrid. Although his forces sustained heavy losses in the Battle of Castleford (as he returned home), Eadred managed to check his rival by promising the latter's supporters even greater havoc if they did not desert the foreign prince.