Serenno was a planet covered in lush forests, mountains and plains. During the Clone Wars, it was aligned with the Confederacy of Independent Systems, the leader of which was the Serenno-born Count Dooku.
In the time of the Galactic Republic, Serenno was home to a noble house of which Count Dooku was a scion. Although Dooku had renounced his status to become a Jedi Knight, he ended up leaving the Jedi Order and came back to Serenno to reclaim his wealth and territory. When Dooku founded the Confederacy of Independent Systems, an alliance of solar systems who wanted to secede from the Galactic Republic, he moved his headquarters to a cliff-side castle on Serenno. The hostility between the Republic and the Confederacy turned into a pan-galactic conflict known as the Clone Wars, and Serenno became a stronghold of the Confederacy. Thanks to a cordon of Confederate warships, the planet was kept insulated from the worst of the Clone Wars battles.
At some point, the Sith Master of Dooku, Darth Sidious, contacted Dooku in his palace via hologram and ordered the count to get rid of his pupil, a Dathomirian named Asajj Ventress. As Ventress had grown too powerful, Sidious feared that she would pose a threat to his own plans. However, Ventress survived Dooku's attempt to kill her. After returning to her people on Dathomir, she came back to Serenno with her fellow Nightsisters Karis and Naa'leth to raid Dooku's palace and exact revenge on him. Nevertheless, the Nightsisters were no match for the count, who used the Force and hurled the intruders out of the palace. After the Skirmish, Dooku received a transmission from the Nightsister Mother Talzin, who offered him to replace Ventress with Savage Opress, a Dathomirian Nightbrother. Upon completion of the deal, Opress was delivered to Dooku on Serenno, and the count started to train him on that planet.
Some time later, Dooku summoned eleven of the galaxy's best bounty hunters, which included Cad Bane and Rako Hardeen, secretly Obi-Wan Kenobi in disguise, to his home planet. He wanted to recruit the best suited candidate to take part in Moral Eval plot to abduct the Supreme Chancellor of the Galactic Republic. In order to do so, Dooku then put the bounty hunters in Eval's Box, a cubical structure hosted on Serenno.
Towards the end of the Clone Wars, Dooku imprisoned the Jedi assassin Master Quinlan Vos at his palace on Serenno. There, the Sith Lord subjected the Jedi to prolonged periods of torture. In order to push him to the dark side, Dooku revealed that his fellow assassin Ventress had murdered Vos' late Master Tholme. Enraged, Vos embraced the dark side and became Dooku's latest Sith apprentice. When Ventress arrived with Boba Fett's syndicate to rescue Vos, he spurned their rescue and sided with Dooku.
- Star Wars: The Clone Wars – "Nightsisters" (First appearance)
- Star Wars: The Clone Wars – "Monster"
- Star Wars: The Clone Wars – "Witches of the Mist"
- Star Wars: The Clone Wars – "Friends and Enemies" (Mentioned only)
- Star Wars: The Clone Wars – "The Box"
- Star Wars: The Clone Wars – "Crisis on Naboo" (Appears in flashback(s))
- Star Wars: The Clone Wars – "Massacre"
- Star Wars: The Clone Wars – "Brothers"
- Star Wars: The Clone Wars – "The Unknown"
- Star Wars: The Clone Wars – "Orders"
- Star Wars: The Clone Wars – "The Rise of Clovis"
- Star Wars: The Clone Wars – "The Lost One"
- Star Wars: The Clone Wars – "The Big Bang" (Mentioned only)
- Dark Disciple
- Tarkin (Mentioned only)
- Battlefront: Twilight Company (Mentioned only)
- "The Crimson Corsair and the Lost Treasure of Count Dooku" (Mentioned only)