" When the builder saw that the work would not be finished, he flew into a giant’s rage. Once the Æsir realized for certain that they were facing a mountain giant, they no longer respected their oaths. They called upon Thor, who came immediately, and the next thing to happen was that the hammer Mjollnir was in the air. In this way Thor paid the builder his wages, but not the sun and the moon. Rather, Thor put an end to the giant’s life in Jotunheim. He struck the first blow in such a way that the giant’s skull broke into small pieces, and so Thor sent him down to Niflhel. "

― Snorri Sturluson , The Prose Edda