The big "Update 1" release for The Elder Scrolls Online adds in the game's first Adventure Zone, Craglorn. Despite Bethesda calling it "Update 1" this is actually the 1.1.2 update for ESO and it includes a lot of new changes and features in addition to Craglorn.
You’ll need allies to take on the new challenges—Craglorn’s quests and exploration are designed for groups of four Veteran Rank 10+ characters. (You can enter Craglorn and play the content earlier than Veteran Rank 10.)

We’ve also added our first Trials in Craglorn, 12-player adventures meant to test even the strongest heroes. In Trials, your team will have a limited number of resurrections to use as you attempt to reach the final boss. If you finish the Trial quickly, you might earn a place on the leaderboards and receive extra rewards!

Another new feature is the Death Recap. This screen will help you understand what contributed to your death and hints that can help improve your performance next time.

Alongside the new content, we’re deploying bug fixes and improvements to make your adventures in Tamriel even better. You’ll see fixes for quests and skill line abilities, updates to systems and quests in Cyrodiil (including bonuses for outnumbered alliances), and much more.

Now, about here is where I would put the changelog for something like this. However, the changelog made this post about 117,000 characters long. That's over double the 50,000 character limit I already raised the site to a while ago. So instead, if you want the very, very full list of changes, you will need to head on over to the Elder Scrolls Online website.

I hope you have a good scroll wheel, because chances are you might need a replacement after going through those notes.