Shortly before the Battle of Yavin, a dark side splinter group called the Prophets of the Dark Side managed to create a copy of Darth Maul. The Prophets themselves stated that "there are techniques to mold a being in every way." As an example to the lesser vassals of Sidious' Galactic Empire and to put an end to the tainted Sith apprentice, Darth Vader, was chosen as the first target for the dark warrior. These dark side worshipers believed Vader to be too much of a Jedi to be a worthy Sith Lord. So they agreed that with Vader out of the way, Maul would once again become Sidious' apprentice and, with the Empire intact, together rule the galaxy.
On the shadowy volcanic moon Kalakar Six, Vader thought he would intercept a Rebel courier with the stolen plans to the first Death Star. Instead, he was met by a false Darth Maul and the observing dark acolytes. After dealing with Vader's stormtrooper guards, Maul then dueled the armored Sith Lord. The two appeared to be evenly matched until Vader cut Maul's saber in two. Unlike on Naboo, this time both ends of the weapon continued to function, allowing Maul to switch to the Jar'Kai style. Due to his size and armor, Vader had a difficult time countering this style, and Maul gained the advantage. Yet, in the final moments of the battle, Vader surprised Maul by stabbing his lightsaber through his own body (and, through proximity, Maul's as well), damaging his own life-support circuits and almost losing his own life in the process. With Maul defeated, the observing acolytes were executed by the newly-arrived Darth Sidious himself for their "treacherous" act towards his rule.