My nagging headcanon is that the DB is a distant descendant of Tiber Septim who carries out the Dark Brotherhood's "To Kill an Empire" contract specifically to restore the Septim dynasty to the Ruby Throne.
I'd like to read a story where the DB, after killing Titus Mede II, steps forward as a Septim heir, using their status as the Dragonborn to supplement their lineage claim (since the Septims were all Dragonborn). This could take place before or after ending the Dragon Crisis and during the Skyrim Civil War (a DB involved in the war could be a wild card for either side if they're also vying for the position of Emperor).
I'm willing to read any direction an A!A takes the prompt, and it could be as short or as in-depth as you prefer. Kinks are welcome if they can be worked in.
Septim!DB - Kills Emperor to reclaim the Empire for Septim bloodline
I'd like to read a story where the DB, after killing Titus Mede II, steps forward as a Septim heir, using their status as the Dragonborn to supplement their lineage claim (since the Septims were all Dragonborn). This could take place before or after ending the Dragon Crisis and during the Skyrim Civil War (a DB involved in the war could be a wild card for either side if they're also vying for the position of Emperor).
I'm willing to read any direction an A!A takes the prompt, and it could be as short or as in-depth as you prefer. Kinks are welcome if they can be worked in.