Deep in the marshes the Tree of Cognizance feeds on whatever living creatures come near it, using very powerful illusions and brute strength. It’s fruits are prized by those that understand the powers they offer.
Evil gives birth to many foul creatures, of these creatures the Negasek have emerged from a womb of darkness and terror. These powerful insect-like creatures radiate the dark force that gave birth to them, born of sheer negative energy, nearly dripping with the foulness of their diabolic nature.
What if a mage passes his powers on to his firstborn son, and a female mage to her first daughter, leaving the parent POWERLESS? A plain mortal, a sorcerer no longer, all wizardly might gone?
Or: what if a female wizard recieves the power of a mage who sires a child with her? Could lead to promiscuous witches and overly careful mages.