Complex sentence: His fate is officially unknown, as the open-ended did not get its sequel; however, as Kurtis was said to play an important role in the Angel of Darkness trilogy, it's likely he survived.
Split into simpler sentences: His fate is officially unknown, as the open-ended did not get its sequel. Although, as Kurtis was said to play an important role in the Angel of Darkness trilogy, it's likely he survived.