Lightwave was apparently another citizen of Zenn-La chosen to become the Herald of Galactus. Most of his history is unknown, but five hundred years in the future he was the father of a half-human adult daughter named Cindy, aka Psionics, and a reformed super-villain working for the New Defenders.
When Earth could no longer sustain the human population, the new Defenders devised a plan to travel back in time and populate the younger, healthier planet Earth. Together, several hundred super-beings joined forces to defeat and capture their Galactus, making him into an engine and power source for what they were planning. Nearly all these heroes died in the effort, reducing the hundreds of new Defenders to Lightwave and a mere half-dozen.
In the early 21st century, the new Defenders plan was modified to take possession of Nu-World, a separate Earth-like construct created by Ted Castle and Alyssa Moy. Lightwave and the new Defenders became the protectors of this Nu-World and the transplanted people.
Over time, however, Nu-World's star became unstable, causing a dramatic time dilation between Earth and Nu-World. Nu-World collapsed into a series of separate kingdoms ruled by different members of the Defenders. Lightwave eventually abandoned Nu-World entirely and returned to wandering the vacuum of space.