Avengers #9 Jan 1965
"Enter, The Avengers!"
The X-Men follow their mentor Xavier to europe where he is hunting down
an old enemy called Lucifer who is responsible for crippling him years ago.
The villain has built a giant thermal bomb and attached it to his heartbeat
to ensure that no one will want to inflict physical harm on him.
Meanwhile, the Avengers are investigating the vibrations Lucifer’s bomb emanates,
The X-Men are forced to fight them in order to prevent them from attacking Lucifer.
Meanwhile Xavier telepathically beats the foe without changing his heartbeat.
After explaining everything to the Avengers
Cyclops and Xavier manage to permanently defuse Lucifer’s thermal bomb.
NOTE: First appearance of Lucifer.
Script by Stan Lee,
pencils by Jack Kirby with
inks by Chic Stone.