Lincoln was raised by his older sister Lorraine (affectionally called Rainy), despite the mere three years' difference between them. Their father left shortly after Lincoln was born, and their mother spent the rest of their childhood bouncing from one shitty boyfriend to the next. She was neglectful at best, abusive on an average day, and at her worst, she let the men she dated do as they pleased to her children. Lincoln would've had it much worse if his sister hadn't taken the brunt of it herself to protect him. 

Rainy started fading away halfway through high school as she carried the weight of their safety and wellbeing on her own. Lincoln was terrified that she wouldn't live long enough to keep her promise of getting them both out of the hell they lived in when she was 18, of losing the only stable person in his life. 

So, he did something incredibly stupid: he sold his soul to save his sister's. At 13 years old, he summoned a demon (after many days of research and failed attempts), and made a deal to get rid of his mother in exchange for his soul. Less than a week later, his mother disappeared, and was never heard from again. Their father was given custody, and things improved drastically. Not that their father was a warm or loving man, but he was at least responsible. 

Rainy went to college, fell in love, and started her own family. She was thriving. Lincoln's soul seemed like a small price to pay for his sister's happiness. He never told her what he'd done--not like she would've believed him, anyway. 

When he was 23, his deal came due, and Lincoln was killed. His soul was dragged to Hell, and he began the horrific process of being turned into a demon.