( The way Dean's expression doesn't seem to shift in the slightest at your memories probably answers Geralt's question immediately. )

No. I mean- yeah, that's where I got it. The memories, back home, however the hell it works, but Lucifer had nothing to do with it. Not exactly.

( Technically everything in Hell is Lucifer's fault as far as Dean's concerned, but for once he's not directly to blame for this particular round of horseshit. )

There was something I had to kill. A demon, except... different. Stronger, older, more annoying. She was- it's called a Knight of Hell. Nothing works on them, not silver, not salt, not the god damn magic knife specifically made to kill demons. Nothing.

( A pause, and then an amendment: )

Almost nothing. We dug up the only blade that would get the job done, but you can't wield it unless you take this.

( Followed by a disgruntled, irreverent slap to the mark with his off-hand. )

The Mark of Cain. Gift-wrapped from the first human on the planet to commit murder. Swell guy. Total douchebag. He said it came with a price, but I didn't exactly have time to get the fine print.