I think SAM is not the final villain, yes it is true sam is the demon king and he will die, but the name of the book is: I will kill the Author. meaning Lucas will kill the person who wrote his tragic fate( not og Author ) Mybe he will destroy the Akashik records for burdening him with this fate.
please pray for lucas upcoming doom there's a hope that he can do the "Magic pen" or "Edit pen" can recreate the quality and description of the item so if his semi-divine artifact can be a divine grade this item may become god artifact so harvest or grind more points