The ongoing Petty Gods Revised & Expanded Edition has a preview up that includes "Tsathoggua" and the "Voormis" and "Formless Spawn." These are statted for Labyrinth Lord (not that one really needs stats for Xathoqqua), but there is good flavor here that could be used for Hyperborea. Nice Clark Ahston Smith tie-ins with all these write-ups, which are quite well done. And it's free from DriveThruRPG.