She somehow has connections to underworld factions. During her stay in Wayrest, she dealt with the Necromancer Lord, Mannimarco. She promised to give him her first born son in exchange for becoming the Queen of Firsthold, Summerset Isles. The deal was accepted and in a short amount of time she departed Wayrest to join King Reman of Firsthold as the Queen of Firsthold. She is known as the Black Queen.
However, not all of the people of Firsthold accepted the new Dunmer Queen. One faction that rejected her rule was the Trebbite Monks, a faction that has a credo for pure Altmer bloodlines on Summerset, and among the royal families most of all. Lady Gialene and her advisor, Kael, manipulated this condition to create open rebellion. Lady Gialene sought to become the Queen of Firsthold herself.
Eventually, the rebellion failed due to a trick made by Morgiah on Lady Gialene. Morgiah told her that a band of Battlemages would face the rebellion, while in fact it was only going to be a group of common archers. The reflection magic that was supposed to reflect the fireballs of the battlemages reflected all of their own healing magic. The wounds from the arrows could not be healed and in the end the rebellion failed.Morgiah inherited much of her mother Queen Barenziah's intelligence and spirit of vengeance.
(PGE3:SI): This nascent revolution in the Summerset Isle has taken many forms. Most constructive, surely, is the acceptance of new cultures and races onto its shores, some occupying positions that would have been forbidden just a century ago. The Queen of Firsthold, for example, is the Dunmer Morgiah, daughter of Barenziah and sister of the King of Morrowind, Helseth. Her children, Goranthir and Rinnala, though half-Altmer, are fully Dunmer in appearance, and stand to inherit the throne.