Except the plot is already "Epic" touching on enemies you would be fighting at 15-20.
Illithids, Githyanki, Dragons, Devils, and the like are not low level enemies, and in fact are an indication that we have practically started at the epic level in enemies and stakes, to where Goblins almost feel like whiplash.
Larian does like to frontload all that or show off, which I'm not a fan of, but fighting them can easily come later at 9+.
We are still actually fighting goblins and lower level enemies and none of that stuff. Except the Githyanki patrol where the dragon conveniently flies off when combat starts.
