20 years ago, the DC comic book hero Firestorm was going through what has been called his "Elemental" stage. That is to say, instead of the familiar "Nuclear Man," he was understood to be a "Fire Elemental," and all of his powers (which were essentially the same powers as before, although he stopped using his previous signature power of changing things into other things) were understood through a lens of having to do with fire. Most fans consider this period a misstep in Firestorm's history, but it did make a few contributions to the myth that were interesting at the time, if all but forgotten now.
One of those contributions was the character of Shadowstorm. Long story short, Firestorm, who was at that time experiencing a crisis of faith, was taken to a land of African gods called Ifé (called the "Living Land" in the story, although this is somewhat at variance with the real Ifé and its African mythology). Ifé was imperiled by shadows which threatened to overtake the land, creating shadow copies of everything--and everyone--they touched. At one point in the story, Firestorm himself was overcome by the shadows. Although he quickly emerged, the shadows spat out a shadow copy of Firestorm, which eventually took the name of "Shadowstorm" for himself. The gods of Ifé finally realized that the shadows were not a force to be fought, but rather an essential part of creation, as necessary as light itself. Although these gods therefore made peace with their shadow-selves, Shadowstorm was not so easily placated. Whereas Bizarro was a kind of "backwards" clone of Superman, Shadowstorm was a clone created from darkness and anger. He considered it a denial of his very being to make friends with Firestorm, and departed swearing that they would remain enemies.
Firestorm soon returned to the mortal realm, and found a sign of hope in a small plant growing in the middle of the desert. After Firestorm departed that area to return to America, Shadowstorm appeared at the same spot, to do nothing more than to destroy the plant simply because it gave Firestorm hope, an act that seemed to promise that Shadowstorm could become a major Firestorm villain for some time to come.
The cancellation of the Firestorm comic only two issues later dictated that this was not to be.
Shadowstorm did reappear about a year later, in the last story arc of Captain Atom's self-titled series. Shadowstorm had apparently never ventured far from the place of his origins, and was slowly turning an entire African city into a city of shadows, burning away all but the anger and darkness each being possesses within themselves. Captain Atom sought to combat Shadowstorm, but was easily overcome himself, and the outcome at the end of the series was left uncertain, at best. The intention was to set up the possibility of Captain Atom's becoming the villain Monarch in the Armageddon 2001 series, but the last-minute decision to turn Hawk into Monarch negated the impact of that story. Another mini-series event, War of the Gods, was taking place at that exact same time, and Shadowstorm made a quick appearance there, basically long enough to take a pot shot at Firestorm and then disappear again.
Shadowstorm has never been seen since.
This gives Shadowstorm the somewhat interesting distinction of being a villain that Firestorm has never truly defeated. He could theoretically still be out there, perhaps having built an empire of shadows and anger where he rules supreme. But, given the several continuity reboots the DC Universe has undertaken in the years since, and the fact that Firestorm has long since left his "Elemental" persona behind, I'm not holding my breath waiting on seeing Shadowstorm again. Indeed, this month marks the 20th anniversary of Shadowstorm's creation, and I would truly be surprised if anyone besides me even notices.
It's too bad, because there was truly some interesting potential here....