Complex sentence: Ultimately, Gawain is unable to end Morgana's life even after he killed Ragnar, but she is however magically trapped by the magic of fairies and he returns to Camelot as a hero to join the Order of the Round Table.
Split into simpler sentences: Ultimately, Gawain is unable to end Morgana's life even after he has destroyed Ragnar, but she gets her soul trapped by the Fairy magic. In the end, Gawain returns to Camelot as a hero to join the Order of the Round Table.