Spoiler
Understandably, this act made much of their kingdom turn against them for real. People tried escaping everywhere, so the monarchists magically trapped as many people as they could in their kingdom before they began brute forcing people to undergo the transformation. What followed was a series of bloody civil wars and the incompletely transformed people rebelling against those who created them, finding ways to escape the kingdom regardless, and desperately studying magic to retain their free will.
Naga live close to dangerous, unknown, chaotically infused lands because they rely on hunting various dangerous creatures to create medication that staves off their ancestral curse. Many of them get injured or killed in this process, which is why many naga study magic to try and lessen their reliance on hunting eldritch abominations, or making their combat more effective to make the hunting safer. They frequently employ manticores to scout and spot for them, because of their evasiveness.
Just as some magi are born more powerful than others, some naga are born without the need to rely on medication to avoid their curse. Laus is one of those, but he doesn't know it. He was somewhat of a government experiment by older naga, to raise a child who was not that different to humans, and was raised without knowledge of his people's past. This was in an effort to make sure that from the little contact humans had with naga, they would never guess that the naga were victims to such a disease.
Laus has unexplainable urges to hurt and kill, but they don't affect him physically like they do with other naga. He's been told that they're just anxiety induced intrustive thoughts and to ignore them. He doesn't like talking about them for obvious reasons.
If a naga falls to their curse, they lose all free will and turn into a thrall of the mysterious monarchy. Usually they will attack and kill as many living things as they can unless instructed to do otherwise by the monarchy. The monarchy can also use them as a conduit to their terrible magics, and force them to open portals to their realm to send forth armies to wreak even more havoc. Nagas do not speak of their history, because they worry that agents of their monarchy might find them and capture them again.
I haven't thought in too much detail about the nature of the monarchy, but
Spoiler
The monarchy claims to love nature and to be helping evolution flow its course, but they all really just introduce a bunch of invasive species into various areas to demonstrate their 'power' as another form of propoganda. They're like evil druids who don't really care about nature, and care more about their own image.