Are D&D Demons zombie proof? I mean you can smoked them with silver (blade, arrows, blunts, and bullets if it has one)
What makes you assume they're "D&D Demons?" There are a lot of other fantasy/game systems in the world besides that one, and nothing canonically saying that the strip in question follows the "rules" of any of them.
If they were D&D Demons, would they not be free to return to their own plane if they wanted to "get off this island" unless bound there by other forces, in which case they also couldn't leave with Safana in any case?
ChowGuy - The LaChoy Dragon - Servant of the Tiger and disciple of the Wanderer The Hall of Wonders - HeavenGames Fantasy Role Playing and Creative Writing Forum.