
This is my conclusion, so take it with a grain of salt..
First of all, do you remember when Lio flashback to the Novel in which OG Baria find documents that said “the Emperor want to change the 4-leaders of NESW and put their own nobles as replacements”? And then Baria get killed because her parents and her sister that is Olor’s Fiancé, agreed to the plan..
We start from there.
So, Olor is one family designated for South’s replacements.
At first, the duke kinda wonder why suddenly the Now-Emperor seems to dare putting his hand on North (the monster business)? Why he dare to woo concubine when the West’s Heiress is his fiancé? All these people think the Now-Emperor is simply immature, but now the letters is found, it becomes clear this fiasco was something that have been started from Late-Emperor.
This is also why Olor family that once was a low noble (so low that the whole Northern Family didn’t even recognised the wandering knight was the Olor’s heir), seems to suddenly raising up to middle-upper rank.
The North hasn’t reached the “truth” that known by Baria (replacing NESW’s leaders) but yes they’re getting closer to it.
And the Ruins that they’re talking about (again this is my take, can be wrong), it seems it was a ruin that have been keeping a secret about how the leaders of NESW come to be. The history of the whole continent.. And of course, it is also possible there will be information of “how to weaken/defeat all leaders of the NESW”.
So yeah, we getting closer to the main plot.

Basically, the imperial family (scheming with Olor family) wanted to explore the northern mountains because they think that it's the origin of of north's power (fangs).
Prof Ardea is being threatened since he was the one writing about that theory regarding the northern mountains. He was supposed to die but Baria saved him in time (this is Baria's 2nd life btw so she knew his fate). They wanted to silence Ardea before he can share it to the Duke.
The late emperor was already working on this plan when he was still alive, including the fact that he had his knights go to the north for "road repairs" (iirc) as an excuse just so they can sneak to the northern mountains. Afterall, this is how Remus (?)(leo's bio father) met Regina, since he was an imperial knight as well.
Empress tigria tbh she doesn't really wanna get involved with the politics and all the imperial drama since he doesn't want to put his children and family (Marquis from the West) in danger. But when she had the opportunity to fuck up the idiot emperor (her husband lol), she led the rebellion and yoinked the throne—that she will hand over to her son after.
i feel like its still messy but i tried to simplify as much as i can. tbh, when i read the manhwa chapter as well, i got confused even though i understood it completely when i read the novel. maybe it was a translation thing?? idk
can someone break down the whole thing about Alor and the northern mountains and the late emperor? I don't get it. and what is the empress' goal in this whole thing?