The Empire of Shadows is a terrorist organization created by Leiko Tanaka with the goal of world domination.
Under the leadership of Leiko (using the title and persona of the Empress Of Shadows), the Empire launched a massive attack against several countries but was stopped by the Vanguard (Beyond The Impossible #64 to #75).
While they would never launch such a widespread attack, the Empire remained active even when Leiko became Minister of Defense for Japan: the Empire would target and kill members of other terrorist organizations, leaving the superhuman agents under Leiko's control the task to damage the Empire to bolster her public image. While the operations of the Empire Of Shadows remain largely confined to Earth, it has played a key role in galactic history more than once.
Their creation Strife convinced Persephone to leave the galaxy
Their technology was used to force Eris into a human body