Daemons are spirits of the underworld, the strongest monster in the game apart from the Necromancer. Blades bounce off them, so defeat them with scrolls or the magic wand. In the final levels, you might want to try avoiding them altogether if possible, to preserve your life-preserving healing potions for the final fight. You can download #Ossuary from https://cyningstan.itch.io/ossuary #ibmpc #msdos #cga