The are many ranks that a Sith must go through to become recognized by his fellow Sith.
List of RanksEdit
Sith Apprentice: A training rank. They are now being trained under a master, but have yet to be realized as a full Sith.
Sith Marauder: The bulk of Sith forces. They are quite powerful with the Force. They are able to train one Padawan at a time. It is also at this rank that they gain their Darth name.
Sith Lord: A powerful Sith rank. This rank is gained after Proving loyalty to the empire and completing missions for the Sith. They have mastered the Dark Side of the Force and are capable of training three Apprentices at a time.
Darth: There are very few worthy of attaining this rank. They have not only mastered the Dark Side, but the Force in general. At this rank, the Sith may be known by their real name or they may pick another name depending on personal preference. A Darth is second only to the Emperor and are able to train as many Padawans as they see fit.
Darth Vader, Darth Maul, Darth Tyrannis, Darth Sidious (Temporarily)
Emperor : There is only one member of this rank. Whoever holds it is leader of all Sith. They are said to be immortal and the cruelest of the Sith. Leader of the Dark council and makes all decisions.
"The Sith must be ruled by a single leader, the very embodiment of the strength and power of the dark side. If the leader grows weak another must rise to seize the mantle."
¯Darth Revan's holocron