Her family was a band of thieves all born in the Deep Depths that lived by the motto of "Lie, Cheat, Steal, and Survive." They supplied in the Tiefling/Drow City - Serica. The group was made up of her Mother Falania, Father Arithorn, Aunt Sala, and Sister Dicala. They gave her as sickle but when she couldn't be intimidating the would instead use her climbing abilities to have her climb buildings and sneak into the second story windows. One day a month before she turned 16 to make they're escape from a house they had robbed her father and mother set fire to the house and surrounding forest. Thalia stopped when she heard the families cries and the snap of a large tree the fire had been eating away at the trunk of. She couldn't do this anymore she never wanted to take anyones life or destroy so much. She fled her family into the burning forest ignoring the fire as it struggled to burn her. Once deep in the forest she she spent the next 6 years learning druidcraft, protecting the forest, and repenting.
Deep in the forest she found a shrine of Sehanine where she took refuge amongst the old building when Sehanine came to her dream and promised to give her power so long she used it to protect.
She found a pendent of Sehanine symbol and now wears it at all times. There was one other hermit, Radagast, living in the forest whose skills at farming were better then hers so in trade for the herbs she would grow and fruits she collected from the tree tops in exchange for the vegetables he grew.
A carriage was passing down an old dirt path that ran through the forest. when it was beset by bandits Thalia couldn't just leave the man to his fate so she stepped in and saved his life. so when he offered her a job she was going to say no when the pendent grew warm and in her head Sehanine said. "Your duty to this forest has long since been fulfilled now go and protect others as you have here."