This is volume 8 of the Avatar Last Airbender series.
Team Avatar find themselves up to their necks in trouble as mysterious forces threaten to destroy land once sacred to the Airbenders! While Aang journeys to the spirit world in search of clues, Toph faces off against her own past!
80 page softcover DARK HORSE COMICS
(W) Gene Luen Yang & Various (A/CA) Gurihiru