Okay I was so wronggg! Chapter 46 is out, although my heart was already tore at chapter 45 and I thought Author would make it all good end but noo! Let season 1 end and boom! A higher cliffhanger that tore my heart for Athhy! Stay strong, wait for Lucas! I'm sure Lucas can do something, stay strong Athyyy!!
I believe you are on the right track with your theory and Lucas might be an attendant of some overseer that is connected to the world tree. Because she would have remembered this character from the original story if he was there and how ancient he actually is.
Okay! *gonna throw out my theory which is half spoilers but may be true or not*
.....
This chapter's translation confirms to me that Claude's brother is still aliveee!!! That dream Athy had was probably a glimpse of the future of the original light novel where he kill Claude by cursing him through Jennette, probably like that blue ribbon she gave to Athyy!! But now, the new reality is that Athhy is now in the place of Claude since that "old man" who used to practice dark magic said to her, "You're cursed"
Aaahh, now that Athy is in favor of Claude, and all Jenette could go near was her instead of her papa, the bro is gonna kill her first before attacking Claude huh!! What's worse is that Lucas is gonna be gone for some time DURING this accident!?
Gahhh, dont dieeee, Athyy!!! *slams head on table* Σ(っ°Д °;)っ （/TДT)/