Solorius Festival, Daevas! Yes, the Atreian equivalent of Christmas is back, and you can join the ongoing Aion celebration through January 5th. You'll find new quests in both Sanctum and Pandaemonium, as well as rewards that include decorative hats, gift bundles, and buff consumables.
Mid-winter and New Year's marks the Year of the Ribbit celebration, and festivities include even more quests and rewards (including new ribbit outfit pieces). The party starts December 22nd and lasts through January 12th.
Finally, NCsoft is turning on the double XP spigot again, this time in honor of Atreia's crafters. Friday, December 17th through Monday, December 20th is a prime time for catching up on any artisan activities you may have been neglecting, as double XP for crafting, essence-tapping, and aether-tapping will be in full effect.