The Elder Scrolls III: Tribunal is the first expansion for Bethesda Softworks' The Elder Scrolls III: Morrowind. It takes place in the temple/city of Mournhold, the capital of Morrowind, located in the larger city of Almalexia. The title refers to the three "Living Gods", known as the Tribunal.
Instead of directly modifying the original game world, the city of Mournhold is only accessible by teleportation. While the city of Mournhold appears to be similar to the open-air towns of the original game, Mournhold is actually akin to an interior room. Players cannot levitate while in Mournhold, because levitation would reveal that the "sky" of Mournhold is little more than a ceiling. Should a player go over the walls of Mournhold (using spells or scrolls such as Scroll of Icarian Flight) they will find the area of Mournhold they were in floating in an endless ocean. The other districts of Mournhold will be absent from the ocean. This was probably done because the original game included only the islands of Vvardenfell, and Mournhold, in the fictional geography of Tamriel, lies on the mainland and a considerable distance inland.
The most notable aspect of Tribunal is the modification of Morrowind's journal system. In the original game, a player's journal can become extremely lengthy and cumbersome. Tribunal allows a player to sort his journal by quest (instead of chronologically sorted) in order to determine what is required for a specific quest. Another notable feature of the expansion is the Museum of Artifacts. The owner of the museum will pay the player half of the value of an artifact (up to 30,000 gold) for one of the very rare artifacts of Morrowind. This is more than the player can get for the artifact at any other store. The museum starts with one artifact (Stendarr's Hammer), and puts the new artifacts on display cases as they are sold to the museum.
Once Tribunal is installed, the plot will start after the player first goes to sleep. The player will be attacked by an assassin, who is later revealed to be a member of the Dark Brotherhood, an assassin's guild that spans Tamriel. To find out more about the Dark Brotherhood, the player will be sent to Mournhold—the capital of Morrowind. Once in Mournhold, the player will have to locate the head of the Dark Brotherhood and complete a series of side quests for the new King Helseth and the Living God Almalexia.
After the completion of one of the side quests, a group of mechanical creatures called Fabricants suddenly attacks Plaza Brindisi Dorom. The creatures emerge from the statue in the middle of the plaza, and after their attack a secret passageway to Dwemer ruins is revealed. Since the creatures are mechanical, it is suspected that the secretive god Sotha Sil is behind this attack. The player then has to investigate the ruins and complete a few more side quests, in order to reconstruct Nerevar's lost sword called Trueflame. Upon acquiring the sword, the player is sent into Clockwork City in order to kill Sotha Sil.
This is possible because the storyline takes place after the events of the main plot of Morrowind, and it is assumed that the Heart of Lorkhan has already been destroyed, thus rendering all the living gods mortal. The player continues to explore all the rooms of Clockwork City, finally arriving to find Sotha Sil dead. When the player tries to leave the room, Almalexia appears and alleges that she had killed Sotha Sil and instigated the attack in Mournhold, in order to gain more power and control over the citizens. It is also possible that Sotha Sil was long dead (as evidenced by his apparent decay), and that having been driven mad by the Heart of Lorkhan, she perceived Sotha Sil's silence as mockery. The player is then forced to kill her before returning to Mournhold.
As the player exits Almalexia's temple in Mournhold, the Daedric Prince Azura reveals that the Heart of Lorkhan drove Almalexia mad and made her hunger for more power, and that mere mortals cannot become gods without consequences. Throughout the later gameplay, only three NPCs are able to believe that Almalexia is really dead; all others will be unable to believe this story and will have a lower disposition if the player insists that this is true.
By destroying the Heart of Lorkhan and killing Almalexia, the player continues fulfilling the Nerevarine prophecies, in particular—the death of the Almsivi Tribunal.