The World of Avlis

Someone seems to be stuck in its deathplane and can't leave because he can't get a dialog

If a DM is using an NPC with mega death magic or dev. crit., How does one know that an NPC has such feat unless one does suffer such attack? it's probably time to reconsider the worth of sticking around. IE, move along or die. Yes but when one does get Dev. crit, it's too late to reconsider. I thin...