From Labyrinthe Wiki
A Mourathal is a close council that advises the Emperor or one who would wish to be Emperor. With the restrictions placed on who could be Senators and provide the Supernatural support required to maintain the sanity of one who must sit upon the Throne of Glass there were often capable beings who whilt not eligble to be a Senator would make excellent advisors. As it so happened the Mourathal of both Emperor Amora's and Emperor Stoneheart's wound up forming the core of their original Senate.
When Empress Truic changed the nature of her Senate in this regard. She appointed a number of "shadow senators" who's sole duty it was to help maintain her sanity as she say upon the Throne, leaving her free to appoint anyone with the character, skill, intellect and loyalty to serve as her Senate.