Who has enough powerful magic.

The Dark Elves' only problem is mana, which is much less than that of the Academy of Magic or the High Elves.

This is only true at the beginning. When I play as the Dark Elves, I often do the following:
First, I choose Iranna. She immediately gets Education (which is never a useless skill) along with Magic Affinity (which already gives 50% more mana at the start).
Second, the primary development task is to get Dark Ritual and Chaos Magic, which later leads to Chaos Lore, which gives +2 to Knowledge and a useful spell. Now you can survive – at least 45 mana (and possibly more, depending on level-ups and Education, if you're lucky).
By this time, you can also build a structure in the castle that gives another +1 to Knowledge.
In addition, Iranna has a bonus for Furies, which is always a plus, especially at the beginning...
The result is a great start with the fastest level-ups, an increased chance of getting a bonus to Knowledge, more Furies at the beginning, which are even stronger, and one and a half times more mana.