Darth Tenebrous held the position of Sith Master to Darth Plagueis. It is believed that Tenebrous conceived the design for the Scimitar, which served as the personal starship for the Sith Lord Darth Maul; however, the official design was created by engineer and starship architect Raith Sienar.
Similar to several other ancient Sith Lords, Tenebrous's name was used for one of the Sith trooper legions within the Sith Eternal, a cult under the leadership of Plagueis' apprentice, Darth Sidious, in 35 ABY. In particular, the 26th Legion was known as the "Tenebrous Legion," and because Sith history was a secret from the rest of the galaxy, only members of the Sith Eternal cultists understood the significance of the name.
The initial mention of Darth Tenebrous within current Star Wars canon appeared in the forty-fourth issue of the magazine Star Wars: Build the Millennium Falcon, which was released by De Agostini around November 4, 2015.
Within the Star Wars Legends continuity, the character of Darth Tenebrous was first presented in "The Tenebrous Way," a short story featured in Star Wars Insider 130, published by Titan Magazines on December 13, 2011. This story was penned by Matthew Stover and visually brought to life by Brian Rood. The character was established as a male Bith and was also identified as Rugess Nome in the novel Darth Plagueis, authored by James Luceno and released in 2012.
- Star Wars: Build the Millennium Falcon 44 (Starship Fact File: Sith Infiltrator — Scimitar) (First mentioned)
- Star Wars: The Rise of Skywalker: The Visual Dictionary
- " The Final Order and the Battle of Exegol " — Star Wars Encyclopedia