He first came to earth to steal its electromagnetic field. On earth he had a human host and would use Thor's transformations from Donald Blake to the thunder god to help him in his own transformation. But he succeeded in transforming himself only halfway back to his original alien form.
Mercurio was created by Gerry Conway and John Buscema in 1973 and first appeared in Thor # 208.
He has fought Thor, Captain Marvel, Captain America, and Quasar. He resided in the Stranger's Laboratory world for awhile.
Major Story Arcs
The Thor War Zarrko
and his faithful Servitor
would come into conflict with the Thor Corps
when he had plans to use his radical time stabilizer to collapse all the time lines into a single entity. The Thor Corps which consisted of Beta Ray Bill
smashed into Zarrko's ship. Zarrko would open up various corridors of time to summon suitable pawns to dispose of the Corps. Various foes of Thor including Mercurio would attack the Thor Corps. Mercurio is easily taken out when Thunderstrike tackles him.
He was last seen as one of the many space villains to use earth as their prison in the Maximum Security saga.
Powers & Abilities
He has super-strength, ability to generate extreme heat and cold, and flight.