Hagalaz

From the White Wolf Wiki, the most complete White Wolf reference

The Hagalaz, first mentioned in Mage: The Ascension, are a group within the Cult of Ecstasy described as violent and tricky Nordic mages. They engage in dangerous traps and rune carving, and their magickal practices seem reminicient of the Norse deity Loki. They see the world as weak and push to overthrow it, intent on replacing it with a Valhallan society.

The infamous William Ethrac is known to be among their members.