Complex sentence: While X-Factor battled its way through the army in Niflhel, Hrimhari caught Rahne's scent on Shatterstar (he and Wolfsbane had fought only a short time ago) and attacked him because he believed that Shatterstar had forced himself on her.
Split into simpler sentences: While X-Factor battled its way through the army in Niflhel, Hrimhari caught Rahne's scent on Shatterstar as he and Wolfsbane had fought only a short time ago. Hrimhari attacked him because he believed that Shatterstar had forced himself on her.