A modder going by the name “DaTeHaCKs” has created a mod for Dark Souls that lets you play as all of the game’s bosses. A new trailer for the mod announced a September 16th release date for it.
While it seems that you can’t play through the entire game as any of the bosses (squeezing the bigger ones such as Kalameet or Ceaseless Discharge through those small doorways would be a bit of a problem) it does let you set up custom matches between the bosses in arenas.
It’s not just bosses that the mod lets you play as, either. You can apparently play as any enemy character in the game. The full details on how all this work are yet to be detailed but for now the added “Arena Mode” certainly allows you to play as all of those characters that killed you so many times.