Board Thread:Off-topic/@comment-26636304-20160103072130/@comment-27150321-20160108204144

Unfortunately Yellow Diamond ended up in a parallel universe  where the Crystal Gems were evil gem/aliens intent on destroying Earth, whilst the Homeworld Gems were trying to save Earth. Inspired by their lust for destruction, Yellow Diamond manages to engineer a way of returning to our universe with an army of evil Crystal Gems to add to her own forces.