The Uncanny X-Men, Vol. 1

Now Strikes... The Sub-Human - Beast and Iceman are out on the town with their ladies when their train is attacked by a subhuman creature. He is Grotesk, the last survivor of a subterranian race, and the X-Men will need to regroup and deal with him in force. Unfortunately, Professor X has other things in mind for himself and Jean.

The Living Diamond - Jack O'Diamonds forces a building to collapse onto Professor X, and then takes Scott Summers with him to convert the rest of his body into diamond rather than just his hands.