Dark ages with Dark Clockwork AU idea.
Where when he gets out of the sarcophagus in reign storm that’s only breaking the initial bindings (and the smallest fraction of his power) and Danny pushing him into the sarcophagus isn't actually sealing him again, if all they had to do was shove him in and close the sarcophagus they would have just needed to shove him when he was distracted and not need a whole war and sealing ritual.Pariah pretends he’s sealed but instead is regrowing his power and breaking the remaining seals. And CW planned all of this.
So when Pariah is sealed CW can’t directly oppose the observants and so has to go along with the sealing even though he is not to pleased having to seal away his husband but does because it’s better than the other timelines where they find a way to permanently seal Pariah.
As soon as he’s sealed CW looks for a timeline that can get Pariah free, a normal ghost can’t free him and it’s going to take a long time for the observants and other ghosts to stop being on edge and keeping a close eye on him so CW decides to be patient he has all the time in the world after-all.
The seals around Pariah’s sarcophagus are intricate a normal host isn’t going to be able to free him, there are other creatures CW could use but getting them into the ghost zone would be tricky as the observants might suspect. That’s when he sees the possibility of a half ghost, in all timelines at least one of Vlad, Maddie and Jack would get ghost powers lab safety was not their strong suit, out of the 3 Vlad is exactly what CW needs, arrogant enough to go for the crown and ring. he’s more than happy... until he notices where that timeline goes and the other half ghost created, Danny becoming half ghost always happens and he’s not used to seeing such a fixed event he can’t help but watch the timelines.
It doesn't take him long to decide yep my kid now, he reminds him a lot of Pariah and himself when they were younger. He has to change his plans a little but he thinks it;’s worth it.
Pariah agrees, after reign storm his and CW bond is back and they can communicate with each other, and Pariah’s ok with waiting a few more years, that’s nothing compared to the hundreds he’s already waited and hey then they get a kid! an Heir! (2 apparently after CW finds out about Dani and CW may have seen a time line where Vlad decided cloning was a bit much and made sure that timeline didn't happen, he wants both his kids thank you very much)
No-one but CW is prepared when Pariah emerges with his full power, poor Danny has no idea what’s happening, he’s trying to figure out HOW pariah is so strong now and is even more confused when he’s called prince of infinite realms.