I just realized I never put this here. Even though I posted it weeks ago in off topic. Might as well blow my load. I believe that Black Mouth is likely the Chosen of 1st that was speaking from the cupcake lore. He also mentions that Aglaecwif is an "old friend" when speaking with SIN on Mars, which I think connects to the cupcake as him being alive still and just as old. That would also mean Black Mouth has a minimum of three Chosen kills. As the cupcake mentions him making Body (3rd), Dark (7th) and Destruction (11th) "bleed". We know for sure, via the changing heart, that the 1st Chosen did indeed kill the 3rd Chosen. Who claimed to be the strongest Chosen of his cycle. So that means Black Mouth also went on to kill the previous 7th Chosen (Beatrice?) and the 11th Chosen. That also means that somehow the Authority trait surpasses the Dark trait. Though, he could've used an army of Body aligned monster proxy or even the 3rd Chosen to wear them down and then kill them. Which could also play a part in Valravn killing the 3rd Chosen.
There's also another thing this update. It's that the previous Chosen of 1st went around targeting those of Body and Memory specifically. Forcing them to submit or killing them if they fought back. Meaning, if Black Mouth is indeed the previous Chosen from the cupcake, his Chosen kill count could actually be above 3. At least, he was probably sniping Body Chosen. Memory got Syla at some point and she's way older than Valravn. So 4th spawns weren't getting made or killed as often. Meanwhile, it seems like the 3rd goes through Chosen a lot. In game, he has the current highest amount of known Chosen. That being 3. They each got killed too. One by the 1st Chosen. The other by Valravn. The recent one by Nyx. And there's really no telling how many Chosen came between when the 1st Chosen killed that one and Valravn killed the other.
If it's indeed true that the 1st Chosen, or Black Mouth in this case killed the previous 7th Chosen. That means Valravn likely went after the 1st Chosen for his very first chosen kill after killing the 3rd and 5th Chosen, or before since he killed the 5th Chosen when Ella was alive. The thing about this though. He failed? Or Black Mouth managed to set up a way to persist even in death. Likely via proxies and the immaterial world, if I had to guess. Also Indra likely killed the 11th Chosen and 8th Chosen before Syla (4th). Reason being that I don't think Chosen from the same twin apostles typically try to kill each other and they seem to target their "distant" cousins more. Even in the cupcake lore, the previous 1st Chosen uplifted the 2nd Apostle in his anti Body and Memory propaganda. So Indra likely didn't go after the 1st Chosen and Valravn likely didn't go after the 8th Chosen. Even though he could. Funny thing about Valravn is, if what I said is true. He only targeted the first six apostle chosen. 1st, 3rd and 5th.
Also, that scene where Memory and Body jumped Authority makes much more sense now in this context lol. Since killing Jake probably triggered the 1st and they wanted to make MC submit to stroke their ego. With both Apostle jumping the 1st instead. Their sibling rivalry is crazy. I don't think any other Apostles beef that much beyond the 7th. Though, I question the 2nd just chilling and watching his twin get jumped. Casually acting like it has nothing to do with him. That's also likely why Black Mouth is eager to get Ella back alive too. Probably so he can use her as his proxy beyond just having her complete her plan.
By the way, the above is only a theory, at the moment. A lot of connecting of dots. I'm not saying Black Mouth is for sure the 1st Chosen from the cupcake. Or that the 1st Chosen actually killed any Chosen beyond the 3rd Chosen of the past. I do think that Valravn might've targeted the 3rd Chosen and the 1st Chosen because of the previous 7th Chosen though. Who possibly might've been Beatrice. The 1st Chosen sort of alludes to killing the 7th Chosen after all. For all we know though, the 3rd Chosen could've been the one fighting the 7th Chosen and they weakened themselves enough for the 1st Chosen to swoop in and kill both. Kind of like how Valravn nearly killing Ella, but he was weakened a lot from losing his heart. In which case, another Chosen could've came and killed both of them. Funny how it could damn near be identical.