Guardians of Oa

The Guardians of the Universe or Maltusians are an alien civilization from DC. They originate from planet Maltus and are the immortal founders and leaders of the interstellar peacekeeping force known as the Green Lantern Corps. At some point they came into contact with symbiotic beings that existed on Maltus, and became immortal, with genius level intellect, and gained godlike abilities. They experimented on the worlds around them. One experiment led to the creation of a new species, the Psions.

In a pivotal moment, billions of years ago, a Maltusian named Krona used time-bending technology to observe the beginning of the Universe. A cosmic lightning bolt hit the machine, causing an explosion. This experiment unleashed evil across the universe and created the multiverse, and an evil antimatter universe. One group of Oans wanted to dedicate their immortal existences to contain evil. This group eventually became the Guardians of the Universe. Another group decided that evil should be destroyed. Traveling to another universe this group became the Controllers. The females, however, saw no need to involve themselves and, since the Oans were by then immortal and had no more need to reproduce, left their mates and became known as the Zamarons.

It was later revealed that the same experiment flooded the beginning of the Universe with entropy causing it "to be born old". Feeling responsible for Krona's actions, the Maltusians relocated to the planet Oa (at "the center of the Universe") and became the Guardians of the Universe. Their goal was simple: combat evil and create an orderly universe. And they acted quickly on that goal. During this period they also changed to their current appearance. They chose Oa as the home of their Central Power Battery.