As a Sith, Count Dooku’s Force lightning is one of the reasons why he’s so dangerous, but it’s a skill he learned long before he became a Sith. One of the main villains of Star Wars: The Clone Wars, Dooku’s lightning is one of his main weapons, much like his master Palpatine. But he learned the skill back when he was still a Jedi, and even used it to save his Padawan, Qui-Gon Jinn.
Dooku is one of only two Sith to use Force lightning in live-action Star Wars but, while lightning is practically synonymous with the Sith, it's not necessary to be a Sith to use it. In the Star Wars sequel trilogy, Supreme Leader Snoke used lightning despite not being a Sith himself, and in Star Wars: The Rise Of Skywalker Rey accidentally cast lightning while not even being aligned with the Dark Side. Even Luke Skywalker considered using lightning. According to the Star Wars: The Secrets of the Jedi reference book, Luke admitted that lightning may be necessary for a Jedi to use when in dire need. Following his confrontation with Palpatine, he saw lightning as the ultimate physical manifestation of the Force.
Related: Why Jedi Don’t Use Force Lightning (But Sith Do)
Dooku first used Force lightning at a young age. According to the audiobook, Dooku: Jedi Lost, he was once abducted for a Dark Side ritual, conjuring lightning to kill his captors and escape. Dooku went on to become one of the greatest Jedi masters, but his ability to use lightning was seemingly a natural talent. Jedi were always forbidden from using lightning, but this would not stop Dooku from using it when he felt he needed to. According to the canon novel Master & Apprentice, Dooku once used Force lightning to save his apprentice, Qui-Gon Jinn from the bounty hunter Shenda
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