Zelashiel, also referred to as Zelashiel the Blasphemer, was a Force-sensitive individual who wielded the dark side of the Force. One of the Force techniques that Zelashiel was proficient in was the ability to drain an individual's essence, a delicate procedure that was exceedingly difficult to use in combat. Zelashiel's teachings eventually were detailed in the Sith Holocron of the Dark Lord of the Sith Darth Revan around the time of the Jedi Civil War.
Sometime between 1000 BBY and 980 BBY, Zelashiel's instructions were commented on in an essay authored by the Sith Lord Darth Bane, who had studied Revan's holocron before destroying it. Many years later, Bane's essay, including his notes on Zelashiel, was added to the Book of Sith, a compilation of historical writings collected in one volume by Darth Sidious.
Zelashiel was first mentioned in the resource guide Book of Sith: Secrets from the Dark Side, which was written by Daniel Wallace. In his third series of endnotes about the book, Wallace mentioned that the character's name was created to sound similar to a theophoric Hebrew name. Wallace also noted that Zelashiel was named such so that the reader could get a sense that the character had experienced a fall from grace. The author further speculated that the character of Zelashiel either preceded the Sith King Adas or was simply a mythical legend.
Zelashiel was first mentioned in the resource guide Book of Sith: Secrets from the Dark Side, which was written by Daniel Wallace. In his third series of endnotes about the book, Wallace mentioned that the character's name was created to sound similar to a theophoric Hebrew name. Wallace also noted that Zelashiel was named such so that the reader could get a sense that the character had experienced a fall from grace. The author further speculated that the character of Zelashiel either preceded the Sith King Adas or was simply a mythical legend.
- Book of Sith: Secrets from the Dark Side