Darth Sidious

Darth Sidious, also known as Emperor Palpatine, was an influential politician and secret Dark Lord of the Sith who achieved power by manipulating the Republic and the Separatists for his rise to power. He is responsible for corrupting Jedi Knight Anakin Skywalker, who became Darth Vader. Along him he created the Galactic Empire.

Death Star project
During the Clone War, Sidious ordered the Republic's Strategic Advisory Cell members including Lieutenant Commander  Orson Callan Krennic and Mas Amedda to create a new super weapon based on the schematics that he had sent them.

Putting Vader to rule
When the Empire rose, Sidious began letting his second-in-command and chief leutenant, Darth Vader, to rule in his name, thus his apprentice became viewed as the Empire's main leader. Krennic came to suspect that since Sidious had let Vader to rule in his name, Vader was not merely a new member of the Emperor's Court, but the two knew each other from earlier on.

Sending a messenger
When the Death Star was finished, Sidious and Vader sent Tarkin to ensure the station is ready as promised and fully operational. In addition he was ordered to test it's destructive power on Jedha, as it's rebel cell known as the Partisans had grown to be a great threat to the Empire's operations on the mining planet.