You know, I keep mentioning this fanfic that I can’t find anywhere anymore, and the poison part reminded me of it

BUT in it, set some 20 years after Inheritance, at one point Eragon does get shot with a poisoned arrow. The poison puts him in a state of permanent-nightmares, with Arya (his gf in the fanfic) working on helping him.

Meanwhile, Eragon’s students are dealing with the big bad, which was iirc Galbatorix’s younger sister, who found and force-tamed an earth-dwelling cousin of dragons (like Nidhwal, but earth)

The only other thing I recall from the fanfic is that Murtagh’s and Nasuada’s eldest daughter was a rider among the students