The Dai-Yukai Genesis

Life, Birth

The Wife of the Third Primordial tricks her husband into allowing female giants to be born by infusing one of her children with a vast amount of primordial essence, and hiding one away from him until it reaches adulthood and proves superior to his own male giants.

Going behind her husband's back and using her magic to change one of her children into a woman with even more primordial essence than the children of her husband the Jotun out of a sense of jealously and anger at having been denied female children, the Wife of the Third Primordial secretely gives birth to a female giant against the wishes of her husband and hides her away until she comes of age.   Once her child grew, she showed her husband the might of her child and tricked him into believing her child was naturally superior with none of the primordial essence used in her husband's children(When in fact, she had used even more). With this, the Third Primordial saw the value of women as warriors, and decreed that no longer would men be his sole champions.