Darth Sidious

"I serve no one's side. Only my own. And soon...my new master."

- Pong Krell, to Captain Rex

Darth Sidious, born as Sheev Palpatine, was the secret Dark Lord of the Sith during the Clone Wars. It was during the Battle of Umbara that Pong Krell revealed to Captain Rex that he had an intention to become Sidious's new apprentice.