Necromancers have little mana, but they can easily replenish it in battle, and they also have various artifacts. If they also get an education, they will have enough mana to cast spells. Dark Elves also have little mana. The point is that light magic is not needed by necromancers.
I completely agree with Alex_R that only the conclusion of this reasoning is clear... that light magic is not needed by the undead.
Please write in such a way that the reasoning itself is also clear.
