Only the strong may rule, this was the way of the Dark Side, and Darth Millennial was about to prove to his master that he was worthy of the title Dark Lord of the Sith, but first, a tremor in the Force draws him to the Unknown Regions of space...
Harry Potter and the Power of the Dark Side by Faykan is a Harry Potter and Star Wars Crossover in which Harry Potter is raised by a Sith Lord.
Has a sequel.  Has a third book rounding it out. 
Harry Potter and the Power of the Dark Side provides examples of:
- Alternate Universe Fic: Harry Potter is a Sith Lord now.
- Bastard Understudy: As is the way of the Sith, Darth Millennial was this to Darth Cognus and Darth Veneficus is his.
- Big Bad: Harry/Veneficus becomes this to the galaxy in the sequel.
- Canon Welding: Instead of happening a long, long time ago the Star Wars universe is now concurrent with the Harry Potter universe.
- Child Soldiers: Darth Veneficus began his Sith training when he was four years old.
- Equal-Opportunity Evil: The Sith are accepting of all species. Respect is gained through power not one's origins. Darth Veneficus finds it pathetic the way the Death Eaters limit themselves with notions of "blood purity" and tells Draco and his fellow Slytherins as much.
- Evil Gloating: Harry/Veneficus gloats to Hermione that he doesn't need to study for exams.
- Evil Mentor: As is the way of the Sith Darth Cognus was this to Darth Millennial who is this to Darth Veneficus who is this to Lord Anguis.
- Evil Versus Evil: Sith versus Death Eaters
- Eviler than Thou: Quirrelmort gets this at the hands of Darth Veneficus.
- Glamour Failure: at the end of the school year Dumbledore catches a glimpse of Harry’s true eye color—the yellow red Sith eyes that come as a side effect of using the dark side.
- Jedi Mind Trick: Darth Veneficus attempts to force persuade his way out of trouble:Professor Snape: As for you, Mr. Potter... Fired curse or no, your actions were a disgrace to the house of Slytherin, and you will serve a detention with me on Saturday, cleaning cauldrons and rethinking how you should have handled the situation...Harry Potter / Darth Veneficus: I will not serve a detention...Professor Snape: You will not... Wait, what did you do to me?!
- Kick the Dog: Darth Veneficus kills a unicorn in order to create a nexus of evil on Earth.
- Laser-Guided Amnesia: Darth Millennial does this to Snape making him forget all about him after he introduces him and his apprentice to the wizarding world.
- Meaningful Rename: Harry Potter is given the Sith name Darth Veneficus and later Draco is given the Sith name Lord Anguis.
- Names to Run Away from Really Fast: Darth Veneficus which means "a sorcerer or a poisoner."
- Original Character: Most of the Star Wars characters.
- Passion Is Evil: The Sith are all about passion—hate, fear, anger, even... love.
- The Power of Hate: Veneficus gets Anguis to channel his hatred during his Sith training.
- Shout-Out: Harry/Veneficus names his owl Traya.
- The Emperor: In the sequel, Harry/Veneficus crowns himself Emperor Veneficus the Eternal of the Neo-Sith Empire
- Training from Hell: Harry/Veneficus has been training in the ways of the Sith since he was four years old.
- Unknown Rival: Darth Veneficus does not acknowledge Voldemort as a true threat for he is clearly no match to the power of the Sith.
- Villainous Rescue: Darth Millennial rescues Harry Potter from the Dursleys. Later Harry/Darth Veneficus and Draco do this for Hermione because Veneficus can see her potential to be a useful Unwitting Pawn.
- Xanatos Gambit: Darth Millennial has several plots running, all of which, no matter the outcome, will advance the cause of the Sith.