[WingedDog]

Well, I also noticed if the first Eater was growing in power and reached about 7000 hp, while the prophet one was still about 500 hp. And it seems like the game consideres the prophet Eater to be my prophet as I'm still unable to make a new one.
Then something else has happened: when the prophet Eater was killed - the same turn the Third Eater U997 has appeared in the same province... Well not third now since prophet is dead - but there are still two indie Eaters in the world, here's screenshot of hall of fame.