Lindra Fren was born with an innate talent for magic, more specifically electricity. At age five, she was already a child protege. Word of her gifts spread until they reached the ears of a band of assassins. This organization was notorious for "recruiting" young and they felt Lindra would be the prefect addition. At age seven, she was kidnapped from her home and forced into their ranks.
During her "training", Lindra was beaten and tortured in an effort to make her more complacent with orders. She gave up the hope of being rescued after her first year with them. Soon, the only thing that pushed her forward was the need to survive.
Once they were fairly sure they had beaten the fight out of her, the band of assassins taught her how to kill without remorse. For the next eight years, Lindra's morals were slowly dying. She used her magic and stealth to murder her targets (often while making it look like an accident). She was given more freedom with every kill as she advanced in the ranks. She probably would have continued that life if it wasn't for her final mission.
The band of assassins still do not know why she chose to warn her target (A high ranking politican in Waterdeep whom had been interfering with their business) and flee from the organization. However, they would hardly care since traitors deserve death. Lindra has spent the last two years in hiding. She has tried to keep a low profile and even swore off magic during this time. However, the fear of being unprepared should someone want her head finally convinced her to re-learn magic spells.