This might sound stupid lol.
I like the idea of the kantus being native to Sera and them being the ones to begin the construction of Nexus.
In the beginning, there was the rift worm that the Kantus tamed or maybe lived alongside, and it created the hollows for them to build Nexus. Given the size of the Rift Worm and its ability to make massive tunnels for the Kantus to move through the Kantus believe the worm to some kind of god like creature and create the religion trinity of warms from it. Anyway, skip ahead a few hundred years or whatever takes your fancy and along comes Nile’s and his search for a cure for rust lung.
Niles discovers the Kantus during his research and discovers that the kantus can heal themselves after sustaining serious injury. Niles captures a kantus and experiments on it in order to find a way to cure rust lung. He combines the DNA of human and Kantus, which has volatile results, which in turn created the Sires. Niles finds adults are just not getting him the results he wanted, so he begins experimenting on children.
After months, maybe years, of trial and error, Nile’s comes across Myrrah whose DNA bonds with that of the kantus. From this Nile’s gets the breakthrough he was waiting for and begin to use what he learned from experimenting on Myrrah and applies it to other his other test subjects. Using this information, Niles finds that the other subjects are not as accepting of the DNA as Myrrah was and as a result the subjects begin to mutate into what is now as the Locust.
Myrrah eventually rebels and the Locust subjects are freed and head into the hollows. The Kantus come across Myrrah and her Locust children, but sense they are close relatives because of the captured Kantus’s DNA being bonded within them. The Kantus take them to Nexus and, sensing that Myrrah is the strongest of the Locust and Kantus they put her at the top of their ranks. The Kantus become teachers of a sort to the Locust and train the Locust to survive the hollows, and over time they live as one and eventually putting Myrrah as Queen of Nexus.
Skip ahead another few months and the Kantus and Locust begin to expand on Nexus under the guidance of Myrrah. Over time, they construct impressive structures in a shorter time span than normal due to their increased strength and Myrrahs ability to guid them and have act as one. Nexus eventually becomes a massive stronghold within the hollows, and the Kantus and Locust continue to live there until the discovery of the Lambent.
The Katus and Locust begin to fight against the Lambent and begin to form an army and create war beasts. They fight continuously, only to find out that everything they are throwing at the Lambent is being taken and used against them. Queen Myrrah and her generals and advisors are out of ideas and losing ground in the hollow. The loss of Nexus has now become a reality, Queen Myrrah believes that if they can’t have the hallows, then no one can. She comes up with the plan to invade the surface and take it for their own, so they may in turn flood the hollows and wipe the Lambent out in one swift action.
There is of course the matter of Adam Fenix trying to come up with a weapon to stop the Lambent and Save the Locust, but that’s for another lore thread lol.
Anyway, that’s my thoughts on what the lore should be close too.