Star War's the Old Republic: Darth Revan's apprentice.

Chapter one:

Twelve year old Ja-ni swung her stick around in the air, pretending she was a Sith warrior on the battlefield against the hated Jedi. She adored the Sith, despite their current condition. Ja-ni! Sari called. Time to work! Ja-ni sighed and nodded. Coming mother. She called back. Ever since her parents became workers for the Sith Empire, the whole family had been forced to work. She didn't realize at the time that what she was in was slavery. Her father, Cordo was a strong, valiant man who did everything he could for his family. Unfortunately he had gotten ill from the fumes and dust, so he took work carving markings into the walls.

Ja-ni and her mother did the dirty work, expanding the corridors and moving boulder's. Ja-ni was raised doing this, so she had become very strong very early in life. She put on her sand gear and picked up her vibroaxe. Day in, day out, chipping away at the rock to build corridors for the Sith Lord in charge, Darth Revan. For some odd reason, she felt a burst of strength whenever the Sith was near her. The odd pureblood was a terror to see, but it wasn't fear. Ja-ni suddenly heard screaming, then a blaster flurry burst down the corridor. Ja-ni clung to the wall, laser's grazing her back and shoulder. When the dust settled, she let go of the wall, her knuckles red from the rock. She saw two figures crumpled on the ground, a man and a woman, her parents. Grief and rage poured through her. She looked up at the three nearby guards and growled. Why did you kill them?! She commanded.

They were caught stealing lightsaber crystals from the wall, which is a crime against the Empire. One robotically stated. Your affiliation with them? Her eyes glowed purple as lightning surrounded her. They were my parents. The Stormtroopers grabbed their throats as invisible hands of darkness choked the life out of them. Then lightning shot out into two of them through the chest, blasting huge holes into them. She picked up her ax and decapitated the third. She dropped the tool and fell to her knees, her power drained. She felt some power, and looked up to see Darth Revan. He extended his hand towards the girl.

Come with me, child. You shall be trained among the Sith as my student. Said Darth Revan. She nodded and bowed her head, and kneeled before Darth Revan.

As you say, Master. Replied Ja-ni.