The dragon showed up to save his descendent. (Lolol if I’m right Kin is going to have a heart attack when he realizes he tried to kill his precious God’s descendant.)
My preferred theory is that they switched the actual Regas and Dragon to protect them, and Regas have been doing that for decades by taking their place and sparing them the abuse and manipulation of the council until the true Dragon/Regas came back. So basically Regas = Dragon and they’ve just been hiding it for protection. But my theory has holes so I’m open to speculation and debate.
Karas' silver eyes might've been something like a gift, so it isn't 100% proof that he is the dragon descendant.
Idk if I would jump onto the band wagon but it wouldn't be too far fetched to assume that before or during the creation myth, the Regas actually ruled over the kingdom and caught the favor of a dragon who then took on the burden of kingship for the Regas, if that makes sense. Maybe Regas were the true dragon-blessed too, while the current royal bloodline were their loyal companions.
But I don't think that Abel's abilities have to be explicitly because he's a dragon or the actual blessed one. Who said only the one with the dragon mojo can have special powers? A true Regas is just as connected to the dragon as the king is in a way, no? At least that's how I read into it. They're both these fated roles that carry a heavy weight, something a bit greater than human. It'd only make sense for a true Regas to be connected to the forest and its residents, after all they are tied to the King's forest (or was it dragon's forest? I forget). How Abel trained in his first life is an indicator of that too if you ask me. Previous Regas were aware of their connection and duty and trained diligently, but that culture was diminished because of the council's monopolization. I'd also like to believe that we just haven't really had the chance to acknowledge the king's dragon blessing much because they've been systematically poisoned and undermined by the council. Karas is pretty busted too if you think about what his eyes can see (he's capable of seeing lies, wasn't he?? I may be talking our of my ass), and his physical health seems just as juiced as Abel's.
But I think we'll find the missing pieces to what we're essentially theorising around soon. There is a big piece missing in this puzzle and I'd like to believe that it's that hidden away weak point that only a true Regas can reveal. A missing piece of the past that will explain why this mystic forest only recognizes the King and his Regas and why these two roles exist the way they do anyway.
Just to play devil's advocate here, that doesn't really disprove that the Regas might be something of a dragon. Like the meanings for Regas and King might've been switched out bc of human bias over the generations, and what was once known as "cursed to love the king" became "cursed to love the Regas". And if once upon a time Regas meant to be the King, then the curse still checks out regardless.
He doesn’t know but I can 100% see Abel crashing out for Karas. Also, I like that theory of “cursed to love the Regas” = “cursed to love the king”. It could be argued that his original body was just a means to an end since he needed to be physically strong to survive that arc of his life. Yes, Karas has the inhuman eyes, but Abel was the one who incarnated. It could be that the two together become the dragon, given the origin story of the dragon in the first place.

My personal theory is that every king has a Regas, but there is only one True Regas, which is Abel and why he reincarnated. Also, I think somewhere along the royal history records, they switched the king and Regas’ ability/origin because Abel shows more signs of being a dragon’s descendant than Karas ever did. I thought that before he even reincarnated. That thing about the animals? Immediately knew it was Abel. And even after he reincarnated that same weird phenomenon keeps happening, where all he has to do is talk about a wild animal and it shows up.
Plus when you think about Abel’s original body, that definitely screamed “Dragon-born” more than anything else. I’m still trying to figure out the silver-eyed dragon dream, but I’m working on that. Also the way Abel’s new body heals and they don’t notice it. And I think the guy in the forest was the actual dragon deity, which is why there was all that fog and kind of adds to the Abel being the dragon descendant theory (cuz they had similar personalities).