So, I had some questions about
@EarthScorpion's homebrew.
Why does your Coadjutor have to be untouchable? His current philosophy is that it is absolutely impossible to kill anyone's Coadjutor no matter what, and trying is horrible because it takes away your nice shiny soul world, all of the characters living in it, and the XP you put into those charms. I mostly don't get why a Coadjutor has to be irreplaceable. There are already charms that let you replace it with your Id or one of your other souls. You obviously need something to regulate your Urge and Torment. The thing is that I don't see why the problem of having a dick of a Coadjutor should never be solved by violence.
It is absolutely in character for a violence focused character who believes himself to have been tricked into being a slave of the Reclamation to try to kill the voice in his head telling him to do stuff. Under ES's rules, this is both possible and verboten. The spirit of the rules says no killing Coadjutors. The letter says that no one from outside of your Empire can enter, and says nothing about your souls killing each other. This is the big thing that I dislike about ES's handling of Coadjutor death. It is unlike Fetich death in that it is philosophically forbidden from happening. Sure, most infernals won't kill their Coadjutors. Sure, having your Coadjutor killed without any way to save it is bad storytelling arguably worse than "Rocks Fall, Everybody Dies." I mostly just feel that the Lord British Postulate exists for a reason, and that I like the way that Exalted as a whole dealt with it: they acknowledged it and included ways for damn near everything to be killed. One of the big complaints about the Deathlords was that they were as completely immortal as the devs could make them.
Firstly, if you don't want to have to put up with a coadjutor, you
don't buy the Merit. Coadjutor 1+ represents being on working terms with your coadjutor. A character who wishes to kill them does not have Coadjutor 1+.
Therefore every Charm with Unwoven (1) or higher as a keyword turns off. Fourth Soul Devil Domain has Unwoven (1) as a keyword.
Therefore no, actually, the mechanics are set up so you can't murder your own coadjutor because trying to murder it indicates you don't meet the prerequisites for the Charm which lets you access it.
That was subtle and entirely deliberate design.
A character who hates their coadjutor and wants them gone has Coadjutor 0, and ignores all this stuff - and so can't use this Coadjutor Charmtech. Unless, of course, they go develop their Id and access it via the alternate path, getting Second Soul Devil Domain, etc. But they still can't murder their coadjutor via it.
My other problem is that there is no discussion about what happens after your Coadjutor dies.
Take it as a given that someone will try to kill her Coadjutor at some point, and that they might just succeed. What happens to her Tiger Empire? Does it immediately disappear destroying everything except the artifacts inside, or does it start to slowly unravel from the center out without the keystone holding it in place? Can the Infernal do damage control and possibly learn a new Heretical Charm to make one of her other souls the linchpin of their Empire?
What about the charms she learned to let her Coadjutor speak through her? Can she repurpose those soul-structures to let her Id or one of her kids speak through her?
Does she immediately enter Torment as soon as the stabilizing factor of her Coadjutor is gone? Does one of her other souls take up the burden of directing her transcendental insanity? If so, what does it make her want to do, if it doesn't have a set of marching orders from the Yozis?
These questions and their answers open up a small niche of Infernal characters. They also eliminate the Lord British Problem. By adding consequences to killing your Coadjutor, you make it possible to kill them in an interesting way while also incentivizing players to protect their Coadjutors. Like all backgrounds, the ST should damn well discuss anything that may have an impact on the player's enjoyment with the player first. That's why backgrounds exist. It doesn't mean that it is absolutely impossible for you to lose your awesome ship, just that it would be lost only if the player is OK with it.
By making Coadjutors killable, you also open up your Tiger Empire to trade with the real world. You allow people you like and trust to enter your world. You allow your Coadjutor to be summoned, and interact with its old friends. You allow so many more things to happen.
If there is some other reason to preserve Coadjutors above and beyond Mentors and Allies and the like, please tell me. I'd love to hear it.
At a mechanical level, if you murdered your coadjutor, every Unwoven-keyworded Charm you have turns off forever. There is no mechanism in place to get back the XP for doing so. So yes, the Devil Domain and the Tiger Empire collapse in on themselves and are permanently destroyed. Any First Circles in there die. Any Second or Third Circles vanish back into the Infernal's mind, as their unmanifested Principles (remember, the Charm Chain for making souls is a General Charm, not a Heretical Charm. The fact that they live in your inner world if you have one is not the default state of that Charm).
And bluntly, I'm not inclined to be sympathetic to PCs who do this when they already had an option for "I don't want to deal with coadjutors, so I won't buy the Merit", so I'd essentially say you've just basically put yourself into NPC status through your self-mutilating act of soul-surgery, removing any way of getting rid of Limit - including entering Torment, so the next time you Limit Break you never leave it. Roughly cutting out a vital element of your soul structure with a spirit-killing Charm does horrible things to Primordials, so it does horrible things to you, and you've just murdered the element regulating Torment and providing a release valve for the stress of Primordial insanity.
So basically if you don't get a replacement before you next enter Torment, you're unplayable and an NPC and the player needs a new sheet.