In 52 BBY, Master Sifo-Dyas accompanied Dooku, Jedi MasterQui-Gon Jinn and Jedi High Council member Jocasta Nu to a meeting on the world of Serenno. After four hours of endless debate, a brief recess was called, and the Jedi were confronted by Damask Holdings magister Hego Damask, in reality, the Dark Lord of the SithDarth Plagueis. Damask aired his concerns for the future of the Republic, and both Dooku and Sifo-Dyas responded to this with their own concerns. Sifo-Dyas was quite stern with his answers and reluctant to agree with what both Dooku and Damask seemed to agree on. Sometime after, Sifo-Dyas and Dooku were present at the Senate Building and met SenatorPalpatine of Naboo, in reality, Damask's Sith apprenticeDarth Sidious.
As his friend Dooku grew disenchanted with the Jedi and the Senate, Sifo-Dyas grew concerned. He became convinced that very dark times were ahead, but the Jedi Council paid little heed to his warnings. In 32 BBY, a gathering was hosted by Supreme Chancellor Finis Valorum on Coruscant. Sifo-Dyas was in attendance alongside JediYoda, Mace Windu, Adi Gallia and Jorus C'baoth. Once again, Hego Damask approached Sifo-Dyas, and once more he openly admitted that a growing darkness was approaching, as he stated to the Jedi twenty years before on Serenno. Sifo-Dyas agreed to Damask's claim and Damask informed him of cloners on Kamino that could grow an army and hold it in reserve until it was needed. The Jedi Master was at first skeptical of this, but was persuaded to think about it.
That same year, Dooku resigned from the Jedi Order after seventy years of service. Before he parted ways with his old friend, Sifo-Dyas said that if Dooku was planning to instigate dissent, he would be one step ahead of him. Following the Battle of Theed, Dooku fell to the dark side of the Force and became the apprentice of Darth Sidious. It was at this time that Sifo-Dyas approached the Kaminoans and requested a clone army for the Republic. With the funds provided by Damask Holdings despite the fact that Hego Damask recently died, Sifo-Dyas paid the Kaminoans. But little did he know that Sidious and Dooku had learned of this and ensured the steps to his demise. Erasing all records of Kamino from the Jedi Archives, the final test provided to Dooku was to murder his old friend. Executing the man, Dooku gained full control of the project for the Sith, using Sifo-Dyas as a cover.[2]
When Jedi Obi-Wan Kenobi traveled to Kamino to investigate the source of the saberdart that silenced SenatorPadmé Amidala's attempted killer Zam Wesell, the Kaminoan Prime MinisterLama Su informed Kenobi that Sifo-Dyas had ordered the creation of a clone army on Kamino at the request of the Senate, in order to help the Galactic Republic. Realizing that a discrepancy in the timeline may exist, Master Kenobi contacted the High Council and revealed the existence of the army.[2]
In 22 BBY, Sifo-Dyas' army was eventually revealed and used at the behest of the Galactic Republic. Three years later, it would be used to destroy the Jedi Order in accordance with a Sith plot a millennium in the making.[2]
In early drafts of Attack of the Clones, the name of the Jedi who contacted the Kaminoans was Sido-Dyas, pointing to a likely early conceptual connection to Darth Sidious. However, interestingly, "Sifo-Dyas" appears in one place, apparently as a typing mistake (as the D and F letters are located next to each other on a QWERTY keyboard) that Lucas later preferred to the original name.[5]
In addition, "Sido-Dyas" was originally only a false identity for Sidious—Obi-Wan Kenobi claimed never to have heard of him, and Mace Windu confirmed that there was no Jedi by that name.[5]
The character's name was changed to Zaifo-Vias in Brazil. The original name is phonetically similar to a vulgar expletive in Brazilian Portuguese, so this was done to prevent confusion.
The first visual appearance of Sifo-Dyas was in The Eyes of Revolution comic featured in Star Wars: Visionaries. The story was written and drawn by ILM concept artist Warren Fu and as a little easter egg, or inside joke, Fu used himself for the face of the Jedi Master. Artist Chris Trevas noticed Fu's likeness in the comic while doing research for his own illustration of Sifo-Dyas in Jedi vs. Sith: The Essential Guide to the Force. For the sake of continuity, and respect for a fellow artist, Trevas contacted Fu to reprise his role for the Jedi vs. Sith illustration as well.[7]
On April 30th, 2013 a new clip showing a piece of an arc of the "Star Wars: The Clone Wars" bonus content shows Plo Koon and his clones looking for a ship wreckage and an old lightsaber inside. It's confirmed that this arc will unveil more details about Sifo-Dyas's last moments of his life.[8]