Galactiac is the Amalgam version of Marvel's Galactus and DC's Brainiac.
Galactiac is the ultimate synthesis between mind and machine. He travels the universe, draining the energy of the planets to recharge his energy cells. He is nearly omnipotent. He keeps a small piece of each planet he destroys for further study.
He came to Earth to attempt to steal it's energies and keep New York City for his study. The Challengers of the Fantastic attempted to stop him, but Galactiac turned their own Ben 'Rocky' Grimm against them, transforming him into the Four-Armed Thing. With the help of Uatu the Guardian, Galactiac was defeated.
He jettisoned his consciousness in the head of his body to regroup, vowing to return.