Ultima VII: The Forge of Virtue is an expansion to Ultima VII: The Black Gate.
Billed as the first 'add-in' rather than 'add-on' expansion, Forge of Virtue places the Isle of Fire in the middle of the Sea of Britain. This is different than other expansion packs in that Forge of Virtue expands the original game rather than extending it by adding more quests or adventure areas that can be accessed externally to the main game.
The Isle of Fire is the location of the final dungeon area in Ultima III: Exodus. The expansion packs backstory tells how Lord British placed tests for the the principles (Truth, Love, and Courage) on the Isle to further the testing of the Avatar.
The Forge expansion allows the player to maximize the Avatar's primary stats as well as to acquire several powerful items, like the Black Sword, an item that would prove quite important in Ultima VII Part 2: The Serpent Isle.
This game is currently available at gog.com and is included in the "Ultima 7 Complete Edition"