The most recent patch introduced a new feature involving the undaunted, Pledges.
Zenimax did a write up on it yesterday on their website which you can find here.
At level 45 you will be contacted by the Undaunted via in game mail. You will be asked to meet them at one of their new “Enclaves” located near the Capital cities.
At these Enclaves you can make a Pledge to take on a certain challenge.
These challenges are like a daily quest requiring you to complete a specific dungeon and will offer optional objectives as well.
The quality of your performance in completing the dungeon will result in a Bronze, Silver, or Gold key.
These keys open up a chest of corresponding quality, giving special rewards.