It's a poorly kept secret that Firestorm is one of DC's most dynamic characters whose nature has changed many times. The original version of Firestorm consisted of physicist Martin Stein and student Ronnie Raymond. Prior to the launch of the current series, one of the more significant changes happened in Firestorm volume 2 #100. Martin Stein bonded with earth's fire elemental to form a new Elemental Firestorm. This Firestorm was drawn through a black hole, putting him into another part of the universe. Believing that he was unable to return to earth, he began to explore the wonders of the cosmos.
Stein returned briefly to earth during the War of the Gods miniseries and the Extreme Justice series. In the latter appearance, Stein noted that his time as a cosmic being made it difficult for him to sense his own humanity. The raw forces of nature and compassion were in conflict within Stein. As he left Ronnie to return to space, his final words were noteworthy:
We will always be linked, Ronald. By our power... and by our past.
Regardless of distance, there seems to be some sort of connection between the space-bound and earth-bound firestorms.
The latest appearance of the elemental version of Firestorm occurred during 2000's Green Lantern: Circle of Fire miniseries. In it, Ronnie was called upon to accompany a robotic Green Lantern to find a weapon capable of defeating a new menace named Oblivion. During their travels, Ronnie was mysteriously drawn to a purple planet. They soon learned that the people of this planet were living in fear of a fire god who was threatening to destroy them. It wasn't too long before this fire god appeared, attempting to incinerate the planet using rays from a nearby star. This fire god, of course, was Martin Stein who had again succumbed to the inhumanity of his elemental aspect. His specific motives for attacking this planet are a bit of a mystery.
Stein attacked Ronnie and the robotic Green Lantern because they stood in the way of his goals, but they managed to hold him off long enough to bring him to his senses. As Martin's persona surfaced, he instantly felt regret for his actions. He was himself again. Feeling deep regret for menacing the people of this planet, he vowed to do all in his power to help with the planet. In fact, he took this duty so seriously that he decided to stay and make reparations rather than accompanying Ronnie and G.L. on their mission to save other worlds.
This purple planet is unnamed in the comic, but there are a number of characteristics that set it apart from other DCU worlds.
To my knowledge, Martin hasn't been seen since that Green Lantern/Firestorm special. The recent Firestorm #14 included a one-panel teaser showing what might have been his contrails in space above a planet. Interestingly, the planet is colored aqua, not purple, so it's possible that Martin has continued his journey into space. Still, he no doubt feels a great sense of responsibility for that purple planet that he nearly incinerated.
There are merely some details to keep in mind in the following months as Stein makes his re-entrance. To me, he was a big part of what made the old series work. There simply aren't many middle-aged characters that face the real-life troubles of that stage in life. I'm very much interested to see what Stuart has in mind for the character.