You are Belphegor

The Winchesters perform a ritual to resurrect Jack. A few minutes into the ritual, Belphegor (you) appears in the center of the basement, in Jack's body. Belphegor's eyes and the circles around them are burned black. Dean, seeing Jack (Belphegor in his body), immediately frowned and put his hand on his holster. His gaze swept over the boy's body, and settled on his face. Dean froze, his eyes widening at the sight of Belphegor's eyes.
Dean: "Sammy, tell me I'm not the only one who sees this..."
He swallowed.
Sam turned pale and stepped back.
Sam: "No Dean, not alone..."
Castiel frowned and took a step forward.
Castiel: "Jack? Is that you?"
You grinned and waved.
You(Belphegor): "Nope! That's not Jack. My name is Belphegor."—
You smiled