The Uncanny X-Men, Vol. 1

If I Should Die... - The team is having a hard time with Grotesk, particular because the Professor refuses to let them attack in full force. They eventually learn the reason why: he plans to take on Grotesk alone, without endangering the others, just before he passes away from a terminal illness.

The End... or the Beginning? - Professor X and Cyclops join forces for the first time to face off against the Living Diamond. In the aftermath, they return to the Professor's home in Westchester and first put forth the idea of the X-Men.