"Trapped: One X-Man!"
While the X-Men tend to the injured Professor X, Magneto and his Brotherhood of Evil Mutants have developed a base on an asteroid orbiting Earth, Asteroid M. They capture the Angel in a skirmish and take him back to Asteroid M, but the X-Men follow. A fight ensues, and Cyclops tries to convince the Maximoffs to switch sides as portions of Asteroid M self-destructs. When the X-Men return, they learn that the Professor's disability was just a ruse to make them more confident on their own. 24 pages (X-668).
First appearance of Asteroid M.
Reprinted in Marvel Super-Heroes (Vol 2) #24 and X-Men: The Early Years #5.