As of December 14th, Elder Scrolls Online will be celebrating its in-universe holiday: the New Life Festival. Much like our world's New Year's festivals, the New Life Festival celebrates the end of one year and the beginning of another. This event will run until January 2.
According to ESO's official website,"In order to join the festivities, acquire the free New Life Festival Scroll from the Crown Store. Use the scroll to find the New Life Herald Breda in a tent just south of Windhelm, Eastmarch. She will give you the initial quest, “The New Life Festival", which will unlock a series of nine uniquely festive daily quests."
Each of the 9 unique quests represents the festivities of one of the nine races. Completing one of these quests for the first time will unlock Breda's Bottomless Mead Mug, which will confer a 100% XP boost for 2 hours; this boost can stack with other boosts. In addition to the mug, you will also receive a New Life Festival Gift Box.
While these usually give assorted random items, like crafting materials, consumable mementos, and Wolfsbane Incense (the Skinchanger style item), this time they will also have a small chance to impart rare items:
Lastly, there will be some new home customizations you can purchase to get it into fit shape for the holiday mood, both of which can be purchased from Heralda Garscroft, the Holiday Achievement Furnisher.
If you're curious to know some extra specifics, like the few places that bonus XP does not apply, then feel free to check out the official blog post, here.