"The magic, or your guilt?" He'd done enough horrible things without a second thought to wander backwards into the abyss of carrying them on his shoulders. No longer able to go back and fix the things he'd broken, the people he'd hurt or the decisions carelessly made without thought or any worry.
It was why Jefferson refused to do any killing. Above all things, what shaped people most in their world, was the power of taking a life. He was neutral on the matter. He was neutral on all things, serving himself and circumstance. Yet the epitome of a character change in all the worlds he traveled began with death. Either taken or given. He had enough guilt to fuel sorrow and depression for many lifetimes to come. The burden of dealing death? That would never leave, no matter what the reason.
All he sought to do was bring Emma comfort and remind her that she wasn't some selfish killer. Had she been, she wouldn't be quite so upset with herself. "It's everywhere. In everyone, and every world. Darkness doesn't ever leave."