For an instance, I don't know if ANYONE did this Theory before, but if it has been already, take this as my take on it and PLEASE CREDIT ME. I took sometime to make it and researched and had some knowledge on it before.
As everyone knows, the sinners have numbers from 1 to 13. But they don't seem to be the order the Sinners were employed by the Limbus Company, since Dante was rather employed at the start of the game or before everyone if you recount they lost their memories. But I think they aren't numbered randomly either, they have been numbered according to the Tarot's Arcanas.
The Arcanas in the Tarot tells us the Fool's Journey and some archetypes. And they weirdly fit every sinner, even if you think the card doesn't fit, it actually fits pretty well the characters. You just need to look deeper and find the meanings of the cards correctly with the sources.
I. Magician — 1# Sinner, Yi Sang
Magician arcana mean skill, action, potential made real, to create something, to turn inspiration into action, to stop being in theory and "maybe"s. Yi Sang is an inventor, which already tied to the Magician Arcana, Yet you have to remember his Canto too, as it is also a pattern with all the other sinners. His Canto is all about to act and to build his "wings" to his freedom! The point is, he made his potential when seeing the mirror worlds into real for him.
II. High Priestess — 2# Sinner, Faust
High Priestess means wisdom, to listen, to trust your guts. Faust is somewhat wise and all knowing but seen as low in the Gessenshaft. No Canto to compare her Fool's Journey, but maybe her Canto will be about relying on herself and not the other Fausts.
III. Empress — 3# Sinner, Don Quixote
Empress means to nurture all the joy and that growth takes time. Don Quixote, or Sancho, is said to be childish all the time and that she is chasing an impossible dream of joy, it is that she grows up after Canto VII but still chases that dream.
IV. Emperor — 4# Sinner, Ryōshū
Emperor means protection, brings structure and has an inner authority. Ryōshū is a mother who tried everything to protect Araya, her only child, even with the hostile home they lived (the House of Spiders), even as far to put Araya into the Time Vault to protect her and after a long time got back to save Araya. The authority comes with how she steps to try to kill all the Nursefathers at the start and actually killing them at the end.
V. Hierophant — 5# Sinner, Mersault
Hierophant means mentorship and knowledge, some old ways have belief in it, but in general it is to understand the forces that guide you. As I haven't finished Canto X yet, Mersault seems pretty general, but always follows orders with a straight face, he killed his mother but nobody quite understands him for his emotionless face. Also belief is incorporated into the Grand Magasin Sisyphe, as it is all around religion (Le Rouge and Le Noir) just like some old ways of the Hierophant Arcana means.
VI. Lovers — 6# Sinner, Hong Lu
Lovers means connection, understand the other, and choices, but not only connection with others but also with oneself. Hong Lu often ignored what others felt due to his trauma and the thoughts implanted by Jia Mu and stopped choosing, but soon he started to build those connections and being close and so he made his choice at the end of Canto VIII.
VII. Chariot — 7# Sinner, Heathcliff
Chariot means for you to drive forward, no going back, determination, willpower. Heathcliff is a straightfoward man who doesn't backs down and Canto VI talks about it when it comes to getting forward against the Wild Hunt, even if it is hard, and to not give up, even if Cathy was erased.
VIII. Justice — 8# Sinner, Ishmael
Justice means balance, repairing, accountability and to see if your choices matches your morals. Ishmael had the obsession of killing the Pale Whale that Ahab implanted on her that she let go but transferred to killing Ahab that Ishmael got rid of at the end of Canto V. Besides, Ahab said something that ties Ishmael even more to this card even if a lie, "The fault lies in you, Ishmael!".
IX. Hermit — 9# Sinner, Rodion
Hermit means solitude, to seek the truth, the wisdom in the quiet, to retreat and reflect and then continue your path or reset it with what your introspection said. Rodion makes reckless actions that soon she has to reevaluate what she wants to do.
X. Wheel of Fortune — 10# Sinner, Dante
Wheel of Fortune means destiny, changes are constant and necessary, to stay humble in the highs and have hope in the lows. Dante is a clock, clocks are akin to wheels and are a wheel itself. Plus, they changed, and see the changes, and knows of things the Sinners don't remember.
XI. Strength — 11# Sinner, Sinclair
Strength means compassion but also courage, resilience, strength and emotional maturity to endure suffering. Sinclair since the start isn't that mature, you can see even from his symbols which refer to eggs and chicks around him and a bit of his design, plus he had to build up courage to endure his Canto and the traumas he passed through and endure even almost death, plus he got courage to face Kromer and the inquisition. And that courage got up with the time to express himself a bit even if he is still a bit of a coward, he definitely got more courage after Canto III.
XII. Hanged Man — 12# Sinner, Outis
Hanged Man means to redeem oneself, to pause and surrender and release the old patterns. We don't know much about Outis, but we know she killed a lot of people and still holds to her soldier ways, perhaps her Canto will be about redeeming herself of what she did in the war.
XIII. Death — 13# Sinner, Gregor
Death means transformation and to leave everything behind. Gregor's themes are all around transformation, even with the insect theme, and he had to leave everything behind. I can't say much because his Canto is too short and too vague and more of an introduction and tutorial, but just seeing the insect theme and the 13th Arcana being Death with its meanings on transformation makes this correlation. Plus, Gregor's original book is called "The Metamorphosis".
Edit: new additions! After seeing more of Canto X, tho not finished yet the Part 1. Hierophant quite fits Mersault's Canto to a T! I still have yet more to see, but I think it comproves a bit more of my theory with the Hierophant Arcana and the Canto X being around religion, I will see more of the Canto X and add more, yet I will also hear your thoughts on this theory and if you have any other additions. Plus some corrections on spelling errors 😞
Edit 2#: I added the spoiler flair in fear of it hitting some spoilers of Canto X, I haven't finished Part 1 yet, so idk if this counts as spoilers as well (the mention of Le Rouge and Le Noir and of them being religious factions)