Reprints X-Men (1963) #34
"War - In a World of Darkness"
The X-Men work to repair Cerebro, but Jean gets a call from Ted that his brother had been kidnapped by Tyrannus and taken to the center of the Earth. Bobby, Warren and Jean follow Tyrannus down into the bowels of the Earth to save Ralph, but on the way down, they run into the Mole Man. The team becomes embroiled in an underground civil war between Tyrannus and the Mole Man and it's Scott and Hank to the rescue.