Darth Phobos was a Theelin Sith Lord of the female persuasion. Her birth occurred on the planet of Korriban, and she existed millennia before the Clone Wars began. Known for her cunning and manipulative nature, Phobos killed numerous members of her Sith order to seize greater power. This led to the remaining Sith turning against her in an attempt to end her life. Surviving this assassination attempt, Phobos established a devoted cult that revered her. She utilized these cultists to attack both Sith and Jedi, earning her the moniker "The Hidden Fear" among the Sith ranks. Ultimately, a combined force of Jedi and Sith brought about Phobos' demise, though her cult persisted until the time of the Fourth Great Schism.
Legends arose concerning Phobos' survival, morphing into an urban myth. Her likeness was integrated into the Jedi Trials as a simulation for the "Trial of Insight." In 3 BBY, this very simulation was combatted by Starkiller, the secret apprentice of the Dark Lord of the Sith, Darth Vader, resulting in Starkiller's victory.

A female Theelin Sith Lord, Darth Phobos, first breathed air on the world of Korriban, a place of ancient Sith burials. This was eons before the Clone Wars. Phobos, a master manipulator, honed her mental abilities, employing the Force to exert control over the minds of the susceptible, compelling them to follow her every desire. She murdered many who were in her way during her pursuit of greater power. In the end, the Sith turned against her, destroying her starship as it was in low-orbit above Korriban. She was believed to be dead, but she had managed to survive and go into hiding.
Over the next few decades, Phobos gathered a fanatical cult that worshipped her exclusively. She sent her acolytes throughout the galaxy to recruit new members and to assassinate both Jedi and Sith leaders without discrimination. Eventually, the Sith began to suspect that Phobos had somehow returned from death and began to call her "The Hidden Fear." Recognizing Phobos and her cult as a significant threat to the galaxy, both factions reluctantly joined forces to stop her. Phobos was eventually killed in a battle against Jedi and Sith warriors, but her cult remained active for a long time afterward, only disappearing around the onset of the New Sith Wars in 2000 BBY.

For centuries, whispers of Phobos' survival lingered, and "The Hidden Fear" became a common subject of ghost stories told by Jedi Padawans. A likeness of Darth Phobos also became a central element of the Jedi Trials that Padawans underwent to become fully recognized Jedi Knights. Appearing within the Jedi Temple on Coruscant, the galactic capital, the Phobos simulation served as the "Trial of Insight," designed to challenge Padawans to face their deepest fears and to learn to see through deception. Even after Operation: Knightfall in 19 BBY, when the Jedi Temple was plundered and left in ruins, the Phobos simulation remained active.
Around 3 BBY, Starkiller, the secret apprentice of Darth Vader, the Dark Lord of the Sith, visited the Jedi Temple as part of his Sith training. Upon reaching the lower Archives level of the abandoned Temple, Darth Phobos' simulacrum confronted him, appearing as Imperial Captain Juno Eclipse, one of the few people for whom Starkiller felt affection, and feigning pain. As Starkiller approached, Phobos attacked him, wielding a double-bladed lightsaber. Throughout their duel, Phobos frequently duplicated and morphed her appearance into that of Eclipse, claiming to have sensed that the Captain's death was Starkiller's greatest fear and that he would hesitate to strike her. Despite this, Starkiller prevailed over Phobos and, after hurling her around the Archives with the Force, prepared to deliver the final blow. Phobos assumed the form of Eclipse one last time, begging the Sith apprentice to spare her. However, Starkiller saw through the deception and stabbed Phobos in the back with his lightsaber, ending the simulation.
By 1 ABY, the technical specifications of the double-bladed lightsaber used by Phobos during her lifetime came into the possession of the Alliance to Restore the Republic. Staff Sergeant Levardio of the Alliance, stationed at Zephyr Base on Rori, the moon of Naboo, offered the specifications for sale to Rebels who demonstrated valor on the battlefields of the Galactic Civil War, allowing the buyer to create their own replica of Phobos' lightsaber after acquiring the necessary resources.
Darth Phobos was a Theelin female with green skin, blue [hair](/article/hair-legends], and yellow eyes. She possessed great skill in manipulating others and readily killed anyone who stood in her way, which ultimately turned her Sith allies against her. Seeking revenge after the attempt on her life, she formed a fanatical cult and slaughtered many Jedi and Sith. Although the Sith initially believed her to be dead, they began to suspect Phobos' involvement in the subsequent murders and named her "The Hidden Fear." After her actual death, rumors of her survival persisted for centuries, and she became a subject of ghost stories among Jedi Padawans. The Phobos simulation that fought Starkiller was determined to uncover his fear and used all her mental powers to confuse him. Phobos discovered that Starkiller's deepest fear was the loss of Captain Eclipse and sensed that she was the only person he truly feared.

Darth Phobos demonstrated remarkable mental abilities, which she used to manipulate the minds of the weak and force them to obey her. The Phobos simulation also showed proficiency with the Force, able to sense her opponent's deepest fears and exploit them. She thrived on phobias and grew stronger from her opponents' fears. During her duel with Starkiller, the simulation of Phobos tricked him into seeing multiple versions of herself and clouded his vision, causing him to temporarily lose his sense of direction. She also unleashed a powerful volley of Force lightning against the aspiring Sith and was skilled in various forms of telekinesis, including Force Repulse and Saber Throw. The simulacrum was adept with her double-bladed lightsaber. She occasionally used Force speed and jump to enhance her agility and could quickly teleport from one location to another.
Darth Phobos made her debut in the 2008 video game Star Wars: The Force Unleashed, with Kari Wahlgren providing her voice. Phobos was featured in one of the Jedi Temple levels exclusive to the PlayStation 2, PlayStation Portable, and Nintendo Wii versions of the game, which were developed by Krome Studios. In The Force Unleashed, entering "HIDDENFEAR" as a cheat code unlocks Phobos as a playable character skin. Additionally, Phobos is a playable character in the duel modes of the Wii and PSP versions, although she must be unlocked first. According to The Force Unleashed: Prima Official Game Guide, Darth Phobos' name is inspired by the word "phobia."
The Force Unleashed left the precise nature of Phobos' appearance in the game ambiguous. The only hint, found in the game's databank entry for "Jedi Trials," was that the simulacrum was projected using the Force. In 2010, the reference book The Jedi Path: A Manual for Students of the Force offered another possible explanation. The book included a description of a holographic projector installed within the Jedi Temple after the Seventh Battle of Ruusan for use during the Jedi Trials. This projector could create holographic simulations of long-dead dark side "monsters." Daniel Wallace, the book's author, later confirmed on his blog that he included this line as a reference to Darth Phobos and Darth Desolous—another Sith simulation from The Force Unleashed—but he intentionally avoided mentioning their names to prevent any potential timeline conflicts.