The Elder Scrolls: Online certainly didn't have a smooth launch with the game being caught behind a subscription barrier. It took some time (and business model changes) to get going, but it seems to now be ticking along. In fact, the game hit the milestone of 10 million players recently, and ZeniMax is holding a bit of a celebration. To show off, for the next week (November 30th – December 6th), the game is free to new players.
It's not just about new players, either. In game, every time you finish a Dungeon with the Dungeon Finder, you will get a Mysterious Rewards Box which can come with all kinds of stuff from Costumes to Pets to Mounts and a whole lot more.
Here is a trailer to show off the game's achievement.