Upon debuting, The Space Phantom claimed he was a member of an unknown alien race, coming to Earth to defeat the Avengers as a means of testing if the planet could be invaded by his people. Taking the shape of several Avengers, he tried to sow dissent amongst their ranks. He was defeated when his power backfired, trying to duplicate Thor, sending him to Limbo.
From: The Avengers #2 (1963)
lowbrowcomics.com 