Yep, the same issue with freezing dice with the Dark Dragon. Also it seems Explode doesn't do any damage to the dragon, only to the player. And 20 Fortified is overkill, with 4 hits per round, which is a lot (2 weapons, 1 blessing), it takes 5 rounds to deplete, which brings the dragon 4 attacks and 9 endurance by that time. My best build by now, still couldn't even lower its health below 600. Maybe I would be able to, if Explode worked, but still won't be enough to defeat the boss.