Metalunan

Metalunans where humanoid people from the planet Metaluna. They where an advanced people with genetically engineered beings called 'Mutos' in servitude to them. They where destroyed in a war with the Zargons, another alien culture, who bombarded their planet till it became so radioactive that it burned like a star. The last of their kind, Exeter, died on Earth where he had been sent on a mission to bring scientists and uranium from Earth to Metaluna for the war effort. He was successful but returned to find the war going very badly with the plan to relocate to Earth about to go underway. The Monitor, the leader of Metaluna, wanted the Earthlings he had brought put through a mind altering process to make them subjects of the Monitor's will. Exeter was not going to allow this as he came to Earth sincerely seeking to recruit aid in the war, and wasn't about to betray the trust he had built. Thus as Metaluna burned he and the Earthlings escaped but Exeter was injured by a rebellious Muto who had stowed away on the ship, and dying. With the Earthlings returned Exeter crashed his vessel into the oceans of Earth.

Biology
Metalunans look very human but have a taller cranium, and thus likely have a bigger brain.