The Emperor is a legendary Dahl SMG. While you have a very slim
chance of finding it at random in any loot cache, you have
increased odds of obtaining it as a loot drop from Assassin Wot,
Assassin Oney, Assassin Reeth, or Assassin Rouf. They can be found
in Southpaw Steam & Power and Digistruct Peak and are
encountered during the side mission 'Assassinate the
Assassins'.