Defeating the quest nemesis causes a “rout”. As a temporary effect, monsters that are part of the normal quest generation flee from you.

Level flag that prevents mapping as long as the local “boss” is alive (nemesis if anywhere in the Quest, demon lords/Croesus on their own levels). Maybe make the ‘nommap’ field 2 bits instead of 1.

Different death texts for if the quest nemesis is paralyzed or sleeping when they die.

Make Quest nemeses death-magic resistant.