Iron Man #55 Feb 1973
"
Beware the Blood Brothers!" First appearance of Thanos.
Drax the Destroyer is a prisoner of Thanos at the evil Titan's Earth-fortress. In an effort to escape, Drax telepathically reaches out to Tony Stark for assistance.
But before Iron Man can come to the rescue, Shell-Head is ambushed by the Blood Brothers! The duo renders him unconscious and transports him to Thanos' desert base.
Thanos confronts Drax and reveals that he has been monitoring him and simply chose not to interfere.
Drax gets lost in his thoughts, which reveal how he had reached Iron Man's mind and told him about Thanos:
He starts talking about Titan, the biggest moon of Saturn, a land that the super computer ISAAC coordinates.
The people of Titan are higly advanced scientists and engineers and are reigned by Mentor and his sons Eros and Thanos.
On Titan, Mentor prepares to aid Drax. As Iron Man is led into Thanos' base he fights back against the Blood Brothers and evades them.
While he is trying to free Drax, Thanos enters and steps on his hand, damaging his right gauntlet.
The Blood Brothers recapture Iron Man, but Mentor and ISAAC send a blast of energy from Titan and through Iron Man's unibeam, destroying Drax's manacles.
Drax and Iron Man quickly best the Blood Brothers. Thanos prepares to destroy his base, but Drax obliterates the self-destruct switch.
Iron Man punches Thanos' head, only to shatter it apart, revealing Thanos has left, leaving a robot duplicate in his place. Suspecting a booby trap, Drax advises Iron Man to exit quickly.
The base is destroyed just as they depart. Drax is certain that Thanos still lives and that he will face him again. He thanks Iron Man for aiding the people of Titan.
Note: This issue also features the first appearances of Drax the Destroyer, Starfox (in a flashback), and Mentor.
Story by Jim Starlin and Mike Friedrich.
Art by Jim Starlin and Mike Esposito.