I feel very honored that you also read my story:) To tell you the truth i have not figured out a lot, i wrote some stuff basically to be inspired and make a series, give each character a personality and a narrative. Yes the idea was for each Apostle to be based on a planet of the solar system but i have not matched each one of them,lol.
I think i will base Hermeticus the Keeper of Secrets at Pluto, he is one of the strongest Mechanicus and kind of an introvert,lol
It's a pretty great story, and I do wonder about the idea of expanding this even more! The artwork gives a great visualisation of the theme and backdrop around it, and I suppose some short stories or fiction of sorts could be neat. Plus, giving each character some backstory as you have done, makes the illustrations even more intriguing to enjoy.
No surprises here, the introvert gets to sit alone on Pluto, sort of like me in a way XD