Three years ago, a mod team by the name of Datehacks released a Dark Souls boss arena mod which, using the leaked debug build of the game, let players control their favorite bosses and slaughter hapless NPCs. At the time, Datehacks couldn't manage much more than staged boss fights, but now the mod team is back with Age of Fire, a revamped mod which not only lets you play as every enemy and boss, but take them anywhere.
You can scale the flying buttresses of Anor Londo as the Sanctuary Guardian, conquer the Darkroot forest as Artorias, or bring light to the Abyss as Gwyn himself. Datehacks shared a bunch of great videos in this Reddit post, but I'm partial to the Gwyn footage myself. Have a look:
Age of Fire is still a work in progress, but it's already capable of much more than the boss arena mod. According to Datehacks' Reddit post, the finished mod will enable players to play as any enemy in any area. The best part is that size doesn't matter: even in tight areas, you'll be able to play as giants like Seath the Scaleless thanks to some camera tricks. I don't know about you, but I cannot wait to see people blast Sen's Fortress to hell and back as Seath and Ceaseless Discharge.
You can't seamlessly travel between maps due to engine limitations, but you can "choose a map and control your chosen enemy and finish the whole map with it," Datehacks says. Naturally, you'll be able to use any of that enemy's attacks as well. I can finally live out my lifelong dream of becoming a wheelie skeleton.
Age of Fire won't work in multiplayer, and it will only work with Dark Souls: Prepare to Die Edition, not the new remastered version. You'll also need the executable from the debug build to get it up and running. Datehacks says a demo version of the mod is coming soon.