What is that?

She wasn't sure what the glowing this within the creature was, but it did draw the eye. She didn't have time to think about it much either because of how swiftly the demon moved. She only had time to follow here instincts and lift her blade. It pierced the creatures chest causing it to shriek out terrible profanities. Black blood gushed from the core and a speck landed on Winter's cheek. It burned and she winced, however, she kept her grip true and kept twisting the blade.

I'm not your prey, you little bastard.