Negaverse is a copy of the Omniverse constructed by Crono-Architect as a safe haven for those under his protection. Separated from all the tension between god and mortal happen in the main Omniverse. But like all thing nice and good in Lord Omniverse. When Shiny get his hand on it, the thing immediately turn into shit.
In the current era, Negaverse is a shit hole devoid of happiness. Filled with Dark Sailor Warrior, Grand Demon God, Dire Wraith, Futabots, Gobots and many breed of deranged Xeno.
Aside from the above fact Negaverse is also a testing ground for Diaclone Project and the place where the first Magical Girl War occur. It play a pivotal role in the foundation of Zen Seibertron Teikoku without Negaverse there will be no Zen Seibertron Teikoku and if there no Zen Seibertron Teikoku there will be no Negaverse in it current state.