Ratings:
Characters 10/10 - they are totally super fleshed out. They react differently to the person and situation they're facing. Not only the mcs, the side characters are also layered with such complexity. Like Leez for example, she seems so dumb, ignorant, naive and carefree but she's so great at faking it that she also fools the readers. She knows what's really happening but she can't really do anything about it because for her, she's just a baggage who's shamelessly mooching off of a person she just meet and is being followed by a deadly sura that can destroy mountains in just merely seconds.
Plot 9.5/10 - the plot is absolutely brilliant and everything has already been planned far out so even though it becomes confusing, you'll rest assured that the author isn't just pulling anything randomly and out of the blue as the plot progresses because she also don't know what direction her own story is going. If you fear that Currygom is going to just drop this just like how every other manhwa authors did to their works or that this'll have a shitty ending, then worry not. A story as complex as this would have taken years to solidify so I'm certain that Curry wouldn't just pull a random ending out of nowhere. The only reason why this isn't a 10 is because the current arc is still progressing and it's confusing af.
Clues/Hints 10/10 - re-reading this masterpiece was really an eye-opener. I noticed that the foreshadowing were already set as early as Chapter 1. I just feel so dumb for not catching most of them. The clues are scattered all around the manhwa. Whether it's hidden in plain sight, in the character's action, in the background, and even the thought process, it's there. Just waiting to be unfold. I had multiple experiences where I was like "oh! So this is the reason why C character was acting strange in B chapter. The clue was already in A chapter! I feel so dumb for not connecting the evidences. 😢" Having a great memory and thoroughly reading the chapters is the best way to read the series. Though, if one is persistent enough, even if you have a faulty memory and poor eyesight like me, then you'll eventually manage..
Art S1 6/10, S2 & S3 8/10 - being the sole author and artist (with not even one assistant) of a complex series such as Kubera for over a decade, I understand why the art didn't improve that drastically like ToG did. Though, it's still great and you can notice the major change. Personally, the art style I loved the most in the series was when it was nearing the end of season 2. I just love the palette/colors used.
If you're going to read this and wants to have an in-depth understanding of Kubera, then try the wiki (tread carefully tho, for it's full of spoilers) or just visit the old batoto discussion forum. The people in there have actively tried to understand and theorise the series. Even moreso than the Line comments which are overflowing with shallow comments. There are even people disliking the translated blogs and the observations of the earlier chapters. They think that those were spoilers when those infos are really super helpful in understanding the series..