The best BigBang 2010 story I've read so far. Hands down.
It needs to be rec'ed like the moment it was posted.

Title: Dictionary for a Dead Language
Author: britomart_is
Pairing: Sam/Dean
Rating: NC-17
Words: 22,000
Summary: Under mysterious circumstances bitterly disputed by the historians, Sam Winchester said yes to Lucifer. Three years later, Lucifer is gone and the familiar landscape that the Winchesters once traversed is a burnt-out ruin of its former self — not to mention the damage done to Lucifer's vessel. Trapped in a grotesque parody of domestic bliss with a brother he no longer recognizes, a shell-shocked Dean has no reason to believe that happy endings exist for men like the Winchesters.

Link to fic.