The Third Legion started their mustering near Anvil. After it had mustered forces, the Legion was immediately posted to the Imperial City to help put down the Moth Rebellion. While fighting the Moth Rebellion, the green recruits earned the Legion the sobriquet The Faithful while besieged in the Hesod Barracks by the Cultists. The Legion marched with Emperor Tiber Septim's honor guard during his re-entry into the capital.
The Third saw action in every corner of the expanding Empire, and is known to have stormed Tarak Shan and pursued kidnappers into the depths of Black Marsh in 2E 861. When the city of Senchal refused to surrender to General Pottreid, he ordered the legion to sack the city, killing Khajiiti men, women, and children. The event was striked from all records of the Empire, removing it from official history.
During an ambush at Black Rocks by the Second Aldmeri Dominion, most of the Legion was killed or captured, with few members escaping. The remnants of the Third Legion made up the core of the new Ruby Legion, and was stationed in the Nibenay Valley for all of 2E 863. In 2E 864, the Ruby Legion was sent to Stros M'kai to post as Amiel Richton's personal guard. Members of the Legion were placed around the island, with many in the palace, dungeon, jail, and streets of Port Hunding. The Ruby Legion defended the palace during the Restless League's invasion under Cyrus the Restless and the Soul Sword. Many of the members were killed or decommissioned afterwards, and Tiber Septim agreed to negotiate peace in the Treaty of Stros M'kai.
- The Elder Scrolls Adventures: Redguard (As the Ruby Legion)