I am looking for a link to the fanfiction DyingStar by gothamcitysyren. It is the 2nd part of the From Grace series. It is a crossover between the Marvel Cinematic Universe and the X-Men. It is about Cassandra Barton, Clint's younger sister who is a mutant. It was posted on Archive of Our Own.
1 Answer
It looks like it is available on Fanfiction.net here.
After settling in London for a failed experiment, Cassandra grapples with the unfair truth that there's no way to get to Asgard. Her past unravels as memories resurface and her life is forever changed by an ongoing legal battle with Tony Stark. But when Jane goes missing for five hours, Cassandra joins the search and the prince of Asgard returns to Earth—and so does hope. • Book #2