Avatar: The Last Airbender--The Rift Omnibus

Avatar Aang and friends honor an Air Nomad holiday that hasn't been celebrated in over one hundred years. But when cryptic visits from the spirit of Avatar Yangchen lead Aang to a refinery operating on land sacred to the Airbenders - they soon find themselves in peril as a dangerously powerful ancient spirit awakens with vengeance and destruction on its mind!