The Epic Story Boost, also known as the 12x XP Event, was a server-wide event that augmented the Experience points earned from all class-specific story missions. Accounts that qualified for the promotion could advance through story missions with an experience point multiplier of 12. The most recent event began on May 4th, 2015 and ended just before the official launch of Star Wars: The Old Republic: Knights of the Fallen Empire on October 27th, 2015.
The Boost was first implemented as a bonus to all subscribing accounts who had pre-ordered the expansion Star Wars: The Old Republic: Shadow of Revan after the expansion's announcement. It was introduced as part of BioWare's effort to attract new players, encouraging a fast-forward through the main class story so as to access the new expansion content faster. The Boost applied to all story missions leading up to the content of Star Wars: The Old Republic: Rise of the Hutt Cartel.
In April 2015, the boost was officially christened as the Epic Story Boost and, at Star Wars Celebration Anahiem, was given a restart date of May 4th, 2015. Until July 15th, the Boost's only given endtime was identified as "Fall 2015", giving the impresion that the event would last a minimum of four months. The Boost was later given an ending date of October 27th, 2015 and applied to all class missions, including the story missions of Rise of the Hutt Cartel.