Evelyn's Tiefling blood didn't manifest in the typical way. Instead it's like a slow cancer warping her appearance and corrupting her mind. An eye patch covers her eye to help hide the deformity her blood has caused. Her covered eye is a darken yellow and the skin around it looks like it was scarred by a fire. But in reality it's her tiefling blood readying it's vessel.
At a young age Evelyn was alone in her happy little halfling shire. The usual community minded halflings weren't sure what to make of Evelyn so even if they didn't mean to, they shunned her for her tiefling blood. This isolation caused her to grow distant from her fellow kin and seeing then through the eyes of hatred. At a young age, she ran away from the shire and ended up in the company of mercenaries. With them Evelyn learned more about the world and learned about Abadar. Might and coin were what matter and if she worked hard no one would look down on her again.
Once she grew of age and heard of the New World, Evelyn decided to make her mark there. Some people told her the riches that could be made and the many opportunities to grow. But the mercenary in her was attracted to what fortunes could be made and the opportunities to grow and become more than a simple mercenary. So Evelyn set out to the New World not knowing what she would find but ready to make her mark.