Tom Riddle makes a bargain with the Marquis. Drabble. Spoilers for HBP.
"Yesss," Tom breathes, hissing, as the Marquis tells him the instructions directly into his ear.
There are no books to give, as none do more than hint at the information. But the Marquis knows how to seal one's life away, and has done so.
Riddle reminds him of someone else, beautiful but cruel.
"You owe me a very big favour," the Marquis warns, and then disappears. Only when he reaches London Below does he allow himself to shudder.