Legion’s Rachel Keller on crafting a romance in a reality-warping landscape

If the various promos and trailers haven’t already clued you in, Noah Hawley’s Legion is going to be kind of a mind fuck, and not just because it’s an “X-Men show” that only skirts its connection to Charles Xavier and his gifted youngsters. The eight-episode series, which premieres February 8 on FX, questions reality…