Complex sentence: The false Etrigan offered them a way out through another portal, but he was merely toying with the dead villains, and when he sent them through a portal, it turned out to be an entrance to Hell.
Split into simpler sentences: The false Etrigan offered them a way out through another portal, but he was merely toying with the dead villains. When he sent them through a portal, it turned out to be an entrance to Hell.