Space Phantom is a Phantun mercenary hired by Thanos to infiltrate the Avengers as a member, and disrupt their activities in order to make sure they don't interfere with his plans to rebuild the Infinity Gauntlet.
Powers and Abilities
The Space Phantom has the power to take on the shape of another person. That person would then be sent to a dimension called Limbo while he was in their guise. Furthermore, Space Phantoms have the ability to take other non-humanoid forms as well.