Complex sentence: Since this first adventure, he has remained with the team.In other adventure he battled his counterpart Karevil escaped and freed the Shadowpact so they can defeate the Pentacle.
Split into simpler sentences: Since this first adventure, he has remained with the team. In a following adventure he battled his counterpart Karevil, whom he escaped from to free the Shadowpact so they can defeat the Pentacle.