Brigid of Emerald is the daughter of Fiona and a Darkovan chieri. The history of that world is much different the novels by Marion Zimmer Bradley, primarily because the Pattern of Emerald and the outlying Shadows were much darker in tone.
The planet Darkover was named by a group of marooned colonists for its dim red sun and cold weather. It was inhabited by the chieri, a dying alien race with psychic and shapeshifting abilities which provided the ability to interbreed with the human colonists. Within five generations, a stratified society resulted from those unions: the psionic-wielding noble descendants of the humans and aliens, ruling the more numerous human servants through the use of their psychic abilities. It was a civilization that remained intact for several centuries through the combined powers of the ruling houses. Power within noble society was gained and held by the strongest wills, and individuals and families struggled for power on the psychic plane while maintaining a peaceful outward existence. Crime (and dissent) was non-existent, because the nobles would continuously mentally scan the populace for criminal activity and rebellion.
The nobles maintained their power even after the rediscovery of the planet by the repressive human Imperial Galactic Empire, and the attempted conscription of the Darkovan psychic powers for the use and expansion of the empire. It was a long struggle, taking over seventy years, but the galactic empire fell apart due to internal political feuds long before they could conquer Darkover, and once more Darkover and its civilization was left alone.
But the eventual downfall and rebirth of the whole civilization of Darkover was imminent, and it was all because of an innocent flower.
A drug distilled from the pollen of the kiereseth flower was known to reduce psychic barriers and stimulate psychic abilities, and it was also a powerful aphrodisiac. It was honored as a holy sacrament, bringing joy to celebrants and healing to damaged psyches, but its use became more prevalent during the years they were fighting off the designs of the empire. As more and more nobles with psychic abilities were needed to fend off the empire, the psychic abilities of the younger nobles were awakened at earlier and earlier ages through the use of the drug. The constant need for its benefits meant that the rare bloom became increasingly difficult to find.
In order to improve it, a Darkovan noble with the rare psychic ability to manipulate genetics tried to crossbreed the delicate flower with other plants, and he succeeded beyond his dreams. One new strain was very potent and very hardy, growing wild in almost any soil, and it bloomed constantly. Any stray breeze would send the raw pollen through the air, casting all who breathed it into a blissful dream state.
In this state, the psychic barriers between the rulers and their servants began to weaken. The stronger minds among the nobles began creating a fantasy world for themselves as a defense against their falling barriers. When the barriers at last failed completely, the weaker minds were caught up in the fantasy world, believing it more real than the real world.