Complex sentence: As Cyclops, Wolverine and Emma Frost break Xorn out of a prison (the prison was being run by some humans who turned themselves into mutants), they quickly learn from Xorn that their powers are waning due to Magneto using the Phoenix.
Split into simpler sentences: As Cyclops, Wolverine and Emma Frost break Xorn out of a prison. They quickly learn from Xorn that their powers are waning due to Magneto using the Phoenix.