So, a couple of days ago, u/PalpitationTop611 posted a reddit post in r/assassinscreed (hub for his posts can be found here) about a ciphered text that can be found in the tower of Saint Denis church in the Siege of Paris DLC. Things gained traction and not long after, a nearby crypt has been found. This crypt contains a second ciphered text along with AC Unity easter egg (you can see the AC Unity: Dead Kings temple through some bars). If you use Odin sense here, then a mysterious ISU text appears and you earn 2 skill points.

Antoine Henry (the guy behind the "Collector's edition" secret that was hiding the Noden's arc bow) indicated, that there is more stuff to do to solve this mystery. Unfortunately, things seem to have cooled down a bit too much on reddit, so I decided to post this here as well to find more help in solving this. To show everything, I will use pictures from a post created by u/gui_heinen (here)

Access the Animus also made a video about this (here) so if you want to look into this secret a bit more, feel free to check out the video. It includes the deciphered versions of the texts found within the DLC and they also translated these texts into English (the text itself is in Latin). I'll be using some translations made by them here as well (along with translations from u/yesrushgenesis2112, who offers a really good level of Latin).

Summary of what we know so far:

The first cipher:

• The first part of the first cipher talks about a spot between Suessionum, Compendium and Paris (which leads to the crypt next to St. Denis) - already solved
• The second part of the first cipher is a bit unclear, as it seems to be talking about some keys ("The first, the second, the third and the last one") - not clear what it actually means
• The text ends with "Octavus" - could be name, but more likely looks like a hint towards... something

The second cipher

• The second cipher talks about the life of Dionysius (also known as Saint Denis), about his execution and about a device he used to manipulate minds - clearly a reference to the Head of Saint Denis found in AC Unity
• A part of the cipher suggests, that someone decided the artifact, but it was messing with his mind and in the end, he "didn't know where to go left" or "which part he is supposed to move left" - this one is a bit unclear, but Antoine Henry used it as a response to someone asking for a bit of help on Twitter, so it's likely important (
  ), he even corrected one of redditors that he in fact meant left and not improper/evil, which is another possible translation of the word sinistrum
• The second cipher again ends with a latin text, now it's "Secundus post tertium, quartum post quintus" which translates to "The second after the third, the fourth after the fifth" - we don't know what it means

ISU text in the crypt:

• It seems to translate to something like "Once seen, it is done" or "One sees, they do" - the theory is that we have to activate the Odin sense here (otherwise we can't even see the message) and this act does... something, we don't know what, it's quite possible this part of the secret is a dead-end meant to end up as an Easter egg, hence the "Once seen, it is done" option of translation
• The second part of the ISU text contains number in HEX format and they can be translated to 782, 3962, 37, 3101 - the purpose of these numbers is unknown

I'll be really happy for everyone who wants to become a part of this joint effort to find out the secret behind the ciphers and the ISU text. If anyone has any ideas, feel free to join the conversation, you are more than welcome. Also, if you have any questions about the stuff that has already been found, feel free to ask here, I'll try to answer as best as I can.

@thesmio the Isu message probably refers to those 2 skill points, because once it is revealed, you gain skill points.

As for the numbers, I already checked @MichalDK suggestion
782: (https://biblehub.com/greek/782.htm), 3962: (https://biblehub.com/greek/3962.htm), 37: (https://biblehub.com/greek/37.htm), 3101: (https://biblehub.com/greek/3101.htm)
which could mean something like "welcome father, consecrate the disciple", but I don't know if it makes any sense.

@bielik01 The idea of Greek concordance or Strong concordance looked really promising, but Antoine Henry shot it down on Twitter

@thesmio
@bielik01

I'm sorry I'm not good at all about the mysteries, but I just found a little thing about the first cipher :

• The text ends with "Octavus" - could be name, but more likely looks like a hint towards... something

Octavus could refer to something related to the 8 number = the 8th : Octava hora = the 8th hour (about 2:00 PM)
I found this at this french page : https://fr.wiktionary.org/wiki/octavus: (https://fr.wiktionary.org/wiki/octavus)
and also https://www.lexilogos.com/latin/gaffiot.php?q=octavus: (https://lexilogos.com/latin/gaffiot.php?q=octavus)

Hope this will give a litlle hint

@azullfr All is good, mate, glad you're trying to help!

Octavus can indeed mean "the 8th" and it's probably the correct meaning, but I don't think it's the final solution, especially because the other cipher contains "The 2nd after 3rd, the 4th after 5th". That's why I said it could be a hint, I think the fact that it's Octavus (the 8th) will be important, but it's not really clear at the moment.

I thought it could either have something to do with years or centuries before Christ (because if you go back in the timeline, you get to the year 0 and then numbers start to add up, so the 2nd century BC happened after 3rd century BC) or perhaps with kings/popes/emperors/bishop (something like there being Charles the 3rd, Peter the 2nd, Anthony the 5th, John the 4th and we'd know we're looking for the person that was the 8th), but neither really seem to lead anywhere at this point

@thesmio

Nice thought about time BC
at the moment, about "quartum post quintus" I was thinking about ... feets
because of "quintus varus", so if you look at your left feet, the 4th toe comes after the 5th one (assuming reading from left to right)

@thesmio I don’t want to discount your efforts or anything, and I applaud everyone who wishes to participate in solving this puzzle, but personally I find this whole matter a deliberate distraction by Ubisoft to take away from the fact that the Siege of Paris expansion is lacking in lots of content and is even incomplete in several respects. I think they simply didn’t want to ‘finish’ developing whatever they started working on under Saint-Denis, or they ran out of time, so they threw a gate on that hallway and made a room with Isu architecture to throw us off.

What was un-finished, you ask? I think the site was supposed to be involved with the Bellatores Dei, which itself was supposed to have a hit-list on the ‘Order’ page, and at some point we would have Eivor wear the Bellatores Cloak again and infiltrate a meeting, kind of like how Kassandra/Alexios did with the Cult of Kosmos in Odyssey. I think the entry-point that was supposed to be used for this story event is in the church and was ‘blocked’ with rocks because of things being unfinished, and the entry-point into the crypt was going to be a ‘back-door’ to get into the meeting, because the real entrance would be overly-guarded or something.

If you look around Francia, you’ll see examples of madness and people having committed suicide. I think this was supposed to be connected to either the Bellatores Dei or another pagan organization using the Isu artifact/Apple of Eden that is in the Head of Saint-Denis. That’s just a side-note theory though... I still need to do a deep exploration of some towns in Francia.

@thenorfolkian Erm, are you trying to say that we are chasing a ghost here and there is no secret? Because if that's the case, then you're wrong because Antoine Henry clearly hid a secret there, just like he hid the Noden's arc.

And while Siege of Paris was overall fairly lackluster, I don't really think any of the things you mentioned were planned to be there. All of that is just theory that has no real substance behind it. Siege of Paris was always going to be a small DLC like Wrath of the Druids, the devs said it. The fact they went for more cinematic introductions and assassinations makes it imo quite clear this was the plan all along.

I also really don't think they were planning to use the crypt for a meeting, because I find it unlikely they would try to recreate the crypt found in Unity. Here, they can say the area around Saint Denis changed a lot, so it looks different than in Unity, but I doubt they were planning to allow us to get into the same location we can get to in Unity because that would either take too much effort for one single cut-scene, or they would make people angry because the place would be different.

@thesmio I never said there was no secret. Clearly, the secret is the message and the two skill points. I said it was a distraction, and I also said I’m not trying to discount this mystery, so please do not take my comments as being dismissive of this endeavor. To repeat: I applaud all who are participating in this.

WotD still had an ‘order’ hit-list with the Children of Danu, a gripping side story that was connected to the expansion’s plot, and a process of discovery for their members, all of which doesn’t exist in SoP, so for players who actually spent money on this expansion, they paid the same as WotD for less actual content. To repeat, it’s not small like WotD, it’s smaller and less substantive.

By the way, Saint-Denis looks different, as it should, because Abbot Suger doesn’t exist yet. Suger and the unknown master mason innovated a new architectural style when renovating the basilica, what would later be called ‘Gothic’ by Renaissance artists.

@thenorfolkian I get what you're trying to say. I still disagree though, the DLC is really lackluster, but it's by design. They went for a more "cinematic" approach with the black box assassinations (and I love that direction, wish we got more) and the Saint Denis secret was done separately from everything else.

Personally, I think they wanted to offer something else, something more cinematic. A lot of recent DLCs for AC have involved a list of cultists or whatever, where you're just ticking off people you kill. It's a fun content, but it could get old quickly and the issue with that setup is that a lot of those assassinations just don't feel like anything special, you're just murdering random people on the streets or in the forts when the game tells you to. Siege of Paris gives much more personality to the people you kill. That really helps the atmosphere a lot, just a shame they really sacrificed quantity for quality and there isn't much to do after you finish the story (unless you count the grindy rebel missions).

And I know about Saint Denis, I was just saying that I'm pretty sure they never intended to recreate Unity's ISU temple (which is below the cathedral) since the two games aren't compatible at all. The overall scale of maps in Valhalla makes everything really small, so recreating an ISU temple from AC Unity which famously decided to stick with 1:1 conversion of real landmarks into the game wouldn't end up well.

Speaking of 1:1 conversion, if AC Infinity sticks with small dense areas, it will help a lot imo. It's cool that you can travel all across Francia or England in Valhalla, but I recently saw some AC Unity gameplay videos and the atmosphere if a fully-modeled Paris is something you never get in the recent AC games.

@thesmio Yeah, I see what you mean about the more cinematic approach... I did enjoy the revivalism of black box missions, but at the same time, I liked the investigative aspect of the newer AC games. I also really missed those murder mysteries from Unity, and it’s kind of too bad that the Reda quests in Origins never really involved any ‘investigating’... just go to the location and rescue or kill whoever, or acquire the item that he rewards you.

You’re right about the 1:1 conversion thing. I suppose if Ubisoft was gonna do an AC Online, it would have been practical to do a 1:1 real world conversion of everywhere to give enough space for the thousands of players, but in a standalone single-player game, this new approach they’ve done has its pros and cons. I do agree that if AC Infinity is going to be like the Helix experience at the beginning of AC Unity, then this new format will help keep multiple areas condensed for the maximum amount of geographical/architectural content.

@thesmio The second part of the ISU text contains numbers in HEX format and can be translated into 782, 3962, 37, 3101 if you have checked these numbers with numbers on a collector's box like Noden's bow numbers on two sides on a collector's box or inside can be a key these numbers marked on the box collectibles must indicate some location on the map. Octavus 8 o'clock seems to indicate the direction to the left

@michaldk I haven't, I don't have the collectors edition. Still, I think the collector's edition has already been "used up" and this mystery will be separate.

Right now, I think we have to find out the meaning of the end of the first cipher, which talks about those 4 keys, of which 3 are close and one stands alone

@thesmio or maybe it is about crosses as 3 keys are close and 1 is lonely in Saint Denis the locations of the crosses

@michaldk Yeah, I think we're missing something like that. I already tried to look at the crosses, but I came up with nothing, perhaps you'll be luckier.

Also, I don't know if you've noticed, but the description of the Durendal swords says "Said to be indestructible and capable of cutting through boulders." and considering the fact Noden's arc was hidden in a boulder and Excalibur had a similar description, I think Durendal could be important in solving this mystery.

Edit: Okay, something even more interesting. Durendal in legend also contained a few relics of saints. The fun part? Among other relics, t supposedly contained a hair of Saint Denis. Interesting coincidence.

@thesmio If you think that the Saint-Denis mystery is effectively a clue pointing to another Isu weapon that has yet to be discovered, and that the Durendal needs to be used, why not go around smashing up ever boulder in Francia at sunrise or sunset? By process of elimination, you might discover the secret weapon before someone else solves the mystery. Sure, it would take a while, but it would be worth it.

@thenorfolkian I tried it in some places, but I really don't have the time to do that across the whole Francia. That's why I made this post as well, there is clearly a secret to be solved and I would love to see it revealed (just like the people who helped during the first few posts on reddit), but it's a long and difficult effort, just like the Noden's arc secret. And there is no guarantee this is the solution either, it could be something else entirely, which is why I created this post here for anyone who might be interested in joining. So far, nothing I thought of lead anywhere, but somebody is bound to discover the true way to solve it and the more people join the effort, the sooner it could be.

@thesmio Interesting is the golden church design of a miniature in the chapel at which Eivor looks at it pensively and at the plaques high in the chapel above this project it looks suspicious

@michaldk Where can you find that?

@thesmio I was going to ask the same thing that you asked @MichalDK. I just now searched Saint Denis and found no such miniature model. It is worth noting though that the ‘construction’ aspect of what’s going on at Saint Denis in the game is totally unhistorical. The Abbey of Saint Denis had been a Benedictine monastery since 632 by the direction of Dagobert I, who was the first king to be buried there. The original crypt is beneath the apse of the church. Renovations were made under Charlemagne, but it wasn’t until 832 that Abbot Hilduin, the Bishop of Paris, ordered the construction of a second crypt, along with a chapel. Hilduin died in 855, but Saint Denis would have continued to be a bustling center of monks and pilgrims, even during the period of the Siege of Paris. For it to appear boarded up, infested with rats, and appearing as if it were in preparations for the experimental changes under Abbot Suger over a hundred years later, is ridiculous.

What really makes no sense, and which is completely unhistorical, is that secret crypt you find with fancy sarcophagi and the passage way that leads to the big corridor with a gate that seems to go down further...