Hey, quick question, did the show or manga actually outline who was giving Uranus and Neptune their orders? They made it explicitly clear that the Outer Scouts had no loyalty to the Moon Princess or anyone else we’ve seen, so it obviously wasn’t the cats. Sailor Saturn was designed as a weapon and was basically repurposed as a Sailor Scout, and Sailor Pluto answered to Time itself, so they weren’t all under the same set of authority. So who gave them their mission, and what made them so dedicated to that mission that they would kill each other and everyone else for it?
 
I have my own headcanon on it, of course. Remember, their first and primary mission was killing Sailor Saturn, which is used as a form of pure destruction. Unchecked, she could annihilate worlds and throw the universe out of balance. Which would, of course, lead to only one thing.
 
Entropy.