I have no idea as I haven't read the 'your eternal lies novel'. It could have a protagonist who is a victim of lies, and an antagonist who is the main source of those lies.
I don't know much about 'your eternal lies novel'. But generally, a novel with such a title might revolve around themes of deception and the long - lasting consequences of lies. Maybe it has a protagonist who is trapped in a web of falsehoods spun by others or by themselves.
The spoilers at the end of a manhwa can be all kinds of things. Maybe a character's fate changes dramatically, or a long-hidden secret is revealed. But without knowing the specific manhwa, it's hard to give exact details.
It's often a combination of cultural influences and artistic innovation. Manhwa art styles can draw from traditional Korean aesthetics while also incorporating modern trends to create a unique look.