The Derth are natural spellcasters within The Quest. Their racial advantages affords them a great boon at all stages of the game, particularly in their defense against spell damage, but their penalties become a nuisance in the earlier stages. However, both become negligible at the later expansions.
"The Derth are gifted scholars, and teachers, and are the most powerful mages of the races. While being stronger mentally they are also physically weaker, and so lack dexterity and endurance".