The "Muir Island Saga" is a five-part Marvel Comics crossover event involving the X-Men and X-Factor, published in 1991.

Professor X returns to his mansion, now in ruins after the Inferno storyline, to use Cerebro, only to find Stevie Hunter on the run from Colossus, also controlled by the Shadow King.

Professor X battles Colossus and frees him from the Shadow King's control, but he is forced to strip away the Peter Nicholas persona he had been using since passing through the Siege Perilous.

Back at the base, Professor X is attacked directly by the Shadow King, using his host body Jacob Reisz, who thinks he has control of all those present, including Cooper.

In the physical world, Forge defeats the still-controlled Psylocke and uses her psychic knife on Polaris to disrupt and sever the nexus.

Val Cooper, returned from Shadow King's control, recruits Polaris, Guido Carosella and Jamie Madrox into a new government-sponsored team to replace Freedom Force.