X-Men Pocket Book #16

In "The Triumph of Magneto!", the X-Men are sent by Professor X to investigate a mysterious entity on Earth, only to find themselves caught in a clash between the Brotherhood of Evil Mutants and a strange, otherworldly visitor. As the Stranger reveals his true nature and his cosmic mission to gather mutants, Magneto seizes the moment—aligning with the alien to escape Earth, leaving the X-Men to grapple with the shocking revelation of his departure.

In "The Supreme Sacrifice!", the X-Men face their greatest threat yet as they're captured by the relentless Sentinels, leaving Professor X to investigate a fallen machine. With the team breaking free and fighting back, it's Professor X’s quick thinking and a shocking act of sacrifice from Dr. Trask that ultimately turns the tide against the sinister Master Mold.