Playing an Acknowledgement game as Prime Minister Esirce (the Grigori tolerant minor leader), I was able to cast Awaken Mother in one of the Archos cities, spawning her in my capital. This also cleared my ability to cast the Grigori world spell. I vaguely recall there was discussion in one of these threads that tolerant leaders aren't supposed to be able to do this (quite obviously), but I can't remember if it is pending for a future patch or if that is supposed to be the case already. In addition, Birthright Regained did not re-enable the ability to use either spell (my own Grigori spell, which I had never used, nor Awaken Mother when Mother died after I completed the ritual). Might be related to it using Awaken Mother.