The Forgotten Hero is the main character of The Elder Scrolls: Legends.
The hero aided the Empire during the Great War between the Empire and the Third Aldmeri Dominion. Due to the deeds of the Forgotten Hero, Lord Naarifin's prophecy was unable to come true, while at the same time, the Forgotten Hero made Lord Naarifin unable to use the Orb of Vearmina, which was used by the Dominion to spy on the Imperial Forces stationed in Skyrim. After the Emperor got attacked and became too weak to lead the assault, the Hero led the charge against the Aldmeri in the Imperial City during the Battle of the Red Ring. Due to the Hero wearing the Emperor's Armor, he led many to believe, including the author of the book The Great War, that he was the Emperor. 
Events of LegendsEdit
The Forgotten Hero was thrown into a fighting pit, to fight against Tyr by the order of Reive. How the Hero got captured is unknown. During the fight, Tyr saw that the hero was a good warrior, and they became companions in order to escape the pit. They fought against a dozen daedric cultists as well as Reive to escape the pit.
Journey to LaanethEdit
After their escape, they journeyed north to meet Laaneth, a sorceress friend of Tyr's. Tyr and the Hero were eventually ambushed by bandits, who demanded a toll, after defeating the bandits, they continued on with their journey, until they were halted by Dominion Guards. When they had defeated the guards, they chose to avoid the roads. When they eventually arrived at Laaneth's house, it was crawling with daedric cultists, who had already started transporting Laaneth away north, to use her to help them bring about The Culling.
Search for LaanethEdit
In order to catch up with the cultists, they needed a ship. The hero and Tyr tried to board one, having it on good authority that the ship was empty. However, the captain of the ship, Swims-at-Night, was aboard and put up some resistance. After a Dominion Guard asked what was going on, on the ship, the captain and the hero realized they had a common enemy. The captain joined the companions and agreed to sail north in search of the sorceress.
Pirates and crashEdit
On the sea, the companions encountered pirates and the daedric cultists, but during a storm the ships crashed onto the shore. Laaneth nowhere to be found and was assumed to have died, either by the crash or by spriggans, who lived close to the crash site. After the companions had beaten the spriggans, they continued their search for Laaneth, they found her, along with some cultists, in an ancient ruin. The hero and his companions rescued Laaneth from the creatures inhabiting the ruins.
Informing the EmperorEdit
Laaneth had learned that the cult was secretly led by Lord Naarifin. To bring about The Culling, he intended to sacrifice all the inhabitants of the Imperial City. In order to reach the Emperor, and inform him of Naarifin's plot, they had to go to Skyrim. Upon their arrival in Skyrim they were told by the local Nords where to find the Legion. While the companions were searching for the Legion, a group of Nordic Imperial deserters blocked their way, the deserters were running from Legate Cassia. When the deserters were beaten, Legate Cassia joined the hero and his companions.
Infiltrating the Imperial CityEdit
After informing the Emperor of Lord Naarifin's plan, the companions went to the Imperial City Arena, posting as gladiators in order to infiltrate the city. After their infiltration, they went through crypts until they reached the White-Gold Tower. Inside Lord Naarifin's study, they learned that Lord Naarifin had used the Orb of Vearmina to track the Imperial army. Lord Naarifin and Reive, however, arrived at the study and the companions had to fight them. Reive had been granted Goldbrand by Boethiah to destroy the companions.
After their succes in the Imperial City, they went back to the Emperor, who had been attacked by assassins. Too weak to lead the assault himself, the Emperor asked the Hero to wear his armor and go in his stead. In the Emperor's armor, nobody would realise that it wasn't the Emperor who was fighting.
The Battle of Red RingEdit
Free from prying eyes, the Legion launched a surprise attack from the west, followed by a similar attack from Cheydinhal. The Hero would then lead the charge to the city gates. Lord Naarifin, however, had already started the Culling, the Hero and his companions had to fight Naarifin and his minions. They were successful disrupting the Culling and retaking the Imperial City.