Gróa appears in the Prose Edda book Skáldskaparmál, in the context of Thor's battle with the jötunn Hrungnir. After Thor has dispatched Hrungnir with the hammer Mjollnir, Gróa is asked to help magically remove shards of Hrungnir's whetstone which became embedded in Thor's head. Unfortunately while Gróa was about her work, Thor distracted her by giving her news of her husband's whereabouts (he had earlier helped Aurvandil cross the river Élivágar), telling her that her husband was now at home. Gróa's spell miscarried and the pieces of whetstone remained permanently embedded in Thor's head.