Complex sentence: After Arioch joins the party, Inuart appears, having sealed a pact with not only a black dragon but the one that murdered Caim's parents, demands that Caim allow him to free Furiae by bringing her to the Empire.
Split into simpler sentences: After Arioch joins the party, Inuart appears, having sealed a pact with a black dragon--the same one that murdered Caim's parents in the past. Inuart demands that Caim allow him to free Furiae by bringing her to the Empire.