Isto é confirmado durante Star Wars: Episódio II: Ataque dos Clones ...
Quando Obi-Wan confronta Jango Fett:
OBI-WAN: Sifo-Dyas. Isn’t he the Jedi who hired you for this job?
JANGO: Never heard of him. I was recuited by a man called Darth Tyranus on one of the moons of Bogden.
E no final do filme:
Count Dooku: The force is with us, Master Sidious.
Darth Sidious: Welcome home Lord Tyranus. You have done well.
Yoda confirma que, com um prefixo de Darth, isso faz dele um Sith:
OBI-WAN: One more thing. Jango mentioned he was recruited by someone named Darth Tyranus. Any idea who that might be?
YODA: With the forename Darth, a Sith he must be.
Citações provenientes de imsdb .