Complex sentence: The three travel to Ganon's tower where Roam and Link defeat the hallucinations there; however, when Zelda is attacked by Agahnim, Roam attempts to defend her and is killed by Ganon.
Split into simpler sentences: The three traveled to Ganon's tower where Roam and Link defeated the hallucinations there. However, when Zelda being attacked by Agahnim, Roam attempted to defend her and was killed by Ganon.