Galactus

Galactus was one of the last survivors of a universe that preceded the current one. Named Galan of the planet Taa, he witnessed the end of the cycle of collapse and rebirth that had defined the infinity of lifetimes of Creation.

Galan was imbued with energy during his actions at the ending of his universe. A powerful entity merged itself with Galan, giving birth to a new one which could survive beyond the ending of time and into a future universe. Thus was created Galactus the Devourer. His hunger is endless and insatiable as he exists to consume life that has grown stagnate and ceased to evolve or develop. Entire worlds are stripped bare, resources and minerals extracted, and biomatter gathered and integrated into the living machine that is his personal conveyance, the World Ship Taa II.

Most races see Galactus as a towering representation of their species. Humans see him as a bipedal giant clad in deeply aubergine armor, though a rare few with exceptional willpower or abilities can pierce the veil and behold his true form.

Galactus often empowers Heralds as advance scouts to locate planets rich in resources, and has had a few of them over the eons.

Starting in the 1990s, Reed Richards sent out a number of probes making use of subspace portals to explore distant reaches among the stars. One probe encountered Galactus and reported back. The Fantastic Four had a brief dialogue with Galactus before contact was lost. His distance from Earth was immense even by the standards of space travel, with near countless systems between Galactus and Earth, so he was not deemed any kind of immediate threat to Earth. As a result this information was held within the Fantastic Four as they moved on to more timely matters.

Of course even Reed Richards can be wrong.