Complex sentence: En route to the North Pole, Aang learns about the genocide against his people when he visits the ruins of the Southern Air Temple, and during the winter solstice he meets the spirit of his predecessor, Avatar Roku, and comes to terms with his responsibilities.
Split into simpler sentences: En route to the North Pole, Aang learns about the genocide against his people when he visits the ruins of the Southern Air Temple. During the winter solstice, Aang meets the spirit of his predecessor, Avatar Roku, and comes to terms with his responsibilities.