Bethesda won’t be challenging the rating (not that it has to).
Though Bethesda Softworks already revealed that The Elder Scrolls Online had received an ESRB rating of Mature, the full description of the game’s sinful activities hadn’t been revealed till now. In the recent product description, the ESRB gave an M rating primarily due to “Blood and Gore, Sexual Themes, Use of Alcohol, Violence.”
While there’s some sexual innuendo at some key points (which you can read about in the full description), the displays of bloody violence seem inline with what we’ve seen in previous Elder Scrolls games. You’ll be severing heads, resulting in tons of blood, and even taking part in drinking games which lend to blurry vision and slurred speech. The ESRB also clearly outlines that being an online game, there will be some user content that can’t be rated.
Bethesda won’t be challenging the rating, and really, given the success of the series despite each title receiving an M rating, it’s obvious they have nothing to worry about. The Elder Scrolls Online releases on March 4th for PC and Mac OS X with Xbox One and PS4 versions due in June.