UNCANNY X-MEN (1963) #53

The Rage of Blastaar! – Jean, Hank and Scott are experimenting with one of Professor X’s ‘mind machines’ when a surge of energy causes them to accidentally release Blastaar from his captivity in the Negative Zone. After that, it’s all out war in the X-Mansion as they struggle to deal with the awesomely powered alien threat! Welcome to the club, Beast – Cyclops, Angel and Iceman rescue young Hank McCoy from El Conquistador, and then he becomes Beast, the fourth X-Man.