oops I traumatised another Star Wars OC
a Sith realised that people would willingly hand over their Force-sensitive kids to anyone they thought was a Jedi. so she killed a Jedi, stole their robes and saber to better impersonate them, and took advantage of her newfound infinite apprentice hack! she stole every Force-sensitive kid she could get her hands on, and when the Jedi caught wind of her scheme, disappeared. she made the kids battle royale to the death to see who was the strongest, as one does.
the fourteen-year-old survivor was renamed Mordex by their new Sith Master. they do absolutely nothing violent with those sharp teeth. don't worry about it. they're also not extremely haunted by a bunch of kids' Force ghosts. don't worry about it!
over the next eight years, their Master added to their facial tattoos to show their progress as an apprentice. when the Jedi found her again, she attacked them and was killed when she refused to surrender. the Jedi tried to reason with Mordex, promising to take them back to the temple on Coruscant to train them, but Mordex believed the Jedi and Sith to be one and the same. Jedi training would simply be a new form of torment.
they mortally wounded one of the Jedi and fled while the other was trying to save their friend. the Jedi decided it was imperative to track Mordex down, and sent several other Knights to find them. after several close calls, Mordex found a planet with strong and very conflicting Force energies, which hid their own Force signature.
when the Clone Wars gained steam, the Jedi were so distracted on the galactic stage that Mordex risked leaving their planet. true to their hypothesis, the Jedi were far too busy to consider hunting them down again, and they were able to move freely. they made no attempt to seek out another Master, and instead put their skills toward bounty hunting.