The Elder Scrolls IV: Oblivion - Fighter's Stronghold

Fighter's Stronghold is the final official add-on for The Elder Scrolls IV: Oblivion. It adds a new quest where you have to rid Battlehorn Castle of marauders. After doing this, the castle becomes the player's property and has to be upgraded to finish the quest. The add-on also adds various new items and NPCs. The PC version was available for free during a limited time after release.