Gen 3
The Gen 3 story focuses on the misadventures of the Dark Siders. The time period equivalent that this story takes place would be around the future, roughly 2200-2300.
The Dark Siders is a small evil legion created and led by Vladmir Kurtz. The idea was originally thought up by Keith Offenheimer as a harmless club but Vlad turned it into... something else. In the Gen 3 story, the Dark Siders only consisted of 7 members: Vlad Kurtz, Jestress Singel, Keith Offenheimer, Gorgen, Sky Deathstar, Anita Wallita and Blietrah. It doesn't gain any more members until later on in the future.
Coincidentally each member represents one of the 7 deadly sins: Vlad being Pride, Jestress being Wrath, Keith being Envy, Gorgen being Gluttony, Sky being Lust, Anita being Greed and Blietrah being Sloth.
The Dark Siders was admitted to the Society of Evil Legions in story Arc 7, where it became recognized as an official evil organization. They currently thrive off of selling weapons to Penguian terrorists in exchange for resources while living in a secret base in the Vi Awki Desert.
Vlad's original intention for the Dark Siders was to create an army of evildoers who would obay his every command, but instead, it ends up becoming some sort of "safe haven" for outcasts and misfits who have been ostracized from society. When he realizes that his evil legion had become more a charity organization, he starts to become much more reluctant to allow others in. Much to Vlad's dismay, many more oddballs, evil or not, would start proposing to join them in order to find a place they finally belong.
GAMMA☆ is a (now disbanded) male idol group that Sky was a part of during his late teen/young adult years. The group was extremely popular across the galaxy, even creating a religious cult legion of fangirls called "Gammagirls". Sky's egotistical persona also started developing here, and it only got worse over time. He doesn't get his "redemption arc" until he meets Keith years later.
Despite (most) of the idol's happy faces, they actually hated working with Sky. They complained that Sky was an attention hog and was treating them poorly, as if they weren't talented enough to perform alongside him. Sky would always flaunt his popularity in front of them and they became miserable working with him. However, their manager dismissed the group's refusal to work with him, as he feared that the band breaking up would destroy thier success. So unfortunately, the idols would have to put up with him for a few years.
GAMMA✰ disbanded after 3 years once the four other idols weren't able to stand their working conditions anymore. Sky moved on to become a solo artist while the others formed their own independent music group. The Gammagirls were devastated by the breakup, but eventually moved on to follow Sky's evolving career. The other 4 faded into obscurity since they were no longer backed by a megacorporation, but that was okay since they were finally free and happy. None of them have ever spoken to or seen Sky ever since then (nor do they want to).