This is going to be a longer story, but I need to work on my other WIPs first! May the Fourth be with you!
Everyone knows about Darth Vader, the Emperor's Right Hand. He is the visible presence in the galaxy of the Sith Emperor, he operates in the light.
But he is not the only Hand the Emperor employs.
Palpatine has a small, dedicated force that work undetected. Unknown to each other, they do the work Vader cannot. They operate in the shadows. They silence those that power and presence would only highlight or worse – martyr.
Of all his Hands, though, Palpatine has one he regards above all others. A man whose unique history will particularly lend itself to this mission.
His Left Hand. Darth Vader's equal and opposite.