The Underground is a world I made up when I was around 12 & rediscovered comic books, fantasy novels & action movies (actually, I never lost interest in action movies but I got big enough to push my older cousins away when they tried to cover my eyes in teh good parts). My corner of reality is a multiverse, which means that there are parallel dimensions. Lots of 'em. The Underground is an organization in charge of the galaxy we call the Milky Way. Their main duties are to keep the timelines relatively straight (as in keep the paradoxes from happening) and keeping the Balance (don't ask, it's complicated and will be explained later). The Sovereigns that are ruling now are humans: The Emperor (Lucas/Darcfyr) & Empress (Kay/Stiletto) & the Triplets (Joyce/Yntenz, Jean[pronounced Zhan]/Jetblayd, Remy[from X-Men]/Hazzardd). Xeno Core is one of 3 Core Warriors, the elite & most trusted of the Underground.
The entire Underground series comes in 3 parts from 3 points of view: Gargoyles, X-Men & Highlander: the Series. I'm pretty sure I'm not allowed to post the last two here but they can be read separately without losing much. If you want all the bitty details, you can go to my homepage and read both POVs. Be warned that I will probably never finish with this reality considering I've got ideas for their grandkids already.