Looks like he's making progress, if he's reading this right. Cas is looking excited, looking maybe hopeful, like he's buying what Dean's selling. Good. Dean wants him to feel disappointed, to feel rejected, from something that should be a sure bet. Something that felt right.

"It wore off. I can tell because, yeah, it was making things pretty bad." He shrugs. "I'm better now, though, except for how I keep thinking about how I'm in there, wanting you, and you're in here... wanting someone."

The dream!Dean starts to move forward, but then stops and backs up a step instead. See? All that room, no incubus magic.

Just a sadistic Trickster.

"Can I come closer, Cas? Please."