Necromance often comes with its own set of rules and limitations in light novels. These rules can be used to explain things like the behavior of the undead. For example, if the undead are mindless in one novel's necromantic system, it could be because the necromancer lacks the skill to give them sentience. These rules contribute to the overall consistency and believability of the world. Also, the origin of necromancy in the world - building can be linked to ancient curses, lost civilizations, or even divine interventions, all of which add depth to the world's backstory.
It can also represent a different form of power. In some light novels, necromancy is a forbidden or rare magic. This makes those who can use it either outcasts or feared and respected figures. This helps to define the social structure within the world. For instance, in a world where most magic is positive and life - giving, necromancy stands out as something different and often darker. It might be associated with certain races or groups, further differentiating them from the rest. And the places where necromancy is practiced, like ancient tombs or haunted forests, add to the overall atmosphere and geography of the world.