Grogg is a winged dragon, centuries old. Originally from China, it leapt the Great Wall, did some maruading then went to sleep for several hundred years before being awoken by a Soviet nuclear bomb test. After a tussle it was put aboard a rocket and launched to Mars.
Mayor Story Arcs
Brought from Mars at some point prior to his second appearance, Grogg was found amongst the monstrous entities being held captive by the Collector. After being defeated again when he was released along with other monsters during a battle between Mole Man and the Collector, he was sent to the Negative Zone.
Under SHIELD's Care
Now under good clean Homeland Security mind control, Grogg is now a mind-control-sub or "agent" of S.H.I.E.L.D.'s “Howling Commandos” division (an elite fighting group of monstrous special operatives), where he acts as transportation for the group.