Her Grace, the Duchess Blackstone
Duchess Blackstone is around 38, beautiful, staggeringly intelligent, and possessed of a stern will, with the breeding and cultural education you would expect of a Duchess. She is deeply connected in the royal court, with a network of spies and allies (including Lady Sofia). She is also well-versed in sorcery, though this is not commonly known.
The Duchess is not specifically evil, but selfish and ruthless and she definitely has interest in taking the crown if it can be done with subterfuge, guile, or concealable treachery. Her army could not match that of the combined kingdom, but perhaps she can make allies and find supporters among the other Dukes, making a military option viable. Time will tell.
In any case, none of that is overt, and Duchess Blackstone is certainly willing to offer whatever assistance she can in averting the impending disaster—after all she does not wish to rule over a wasteland. This makes her an initial ally, but naturally she will try to turn any resulting circumstances in her own favor.
The Duchy of Blackstone is named for Blackstone Keep, a fortification above the city of Sangenoir. That area has rich deposits of coal and cinnabar, making it politically important and wealthy.