 Specific valkyries are mentioned on two runestones ; the early 9th century Rök Runestone in Östergötland , Sweden , and the 10th @-@ century Karlevi Runestone on the island of Öland , Sweden , which mentions the valkyrie Þrúðr . On the Rök Runestone , a kenning is employed that involves a valkyrie riding a wolf as her steed : 
