Bringing this over from another thread:
Something needs to be done about the Grigori tech tree. Namely, Honor and Deception. There is honestly no good reason for the Grigori to be able to research these techs, and allowing them to found Empyrean/Council of Esus essentially kills those religions, especially CoE which becomes virtually unspreadable if the Grigori found it.
My recommendation (and what I did in my personal modmod) is this: Move Overcouncil and Undercouncil membership (not founding) to Way of the Wise/Wicked, and move Defensived Pacts to Military Strategy. With those two changes, the Grigori can safely be banned from researching Honor and Deception, thereby preventing them from killing those two religions. They lose out on the Trojan Horse, but it's not a unit that really makes sense for them/is useful for them anyway.
Also, moving council membership to Way of the Wise and Way of the Wicked makes it much harder for the council founder to dominate the council, since there is much less of a chance you will be the only member when you found the council.
Lastly, although this is more of a nuisance and less game-breaking, it would be nice if the Grigori didn't have to research an expensive and completely useless tech (Theology) in order to be able to research the tech for Immortals, which are quite a necessary unit for them (Immortal-Adventurers ~are~ your late game military in many cases).