S1·E51 To the Place Where the Wind Blows

The episode starts with Zed getting enveloped in Tusker's power; Tusker releases himself and uses Zed's body and spread his wings to reveal his true form. While Zed is inside the endless abyss in Tusker getting lectured about how humans are bad because they want power, all the spirits get released. In the end Tusker is defeated, spirits go back to where they came from, Zed tries to attack Amil Gaoul but ends up shifting and merging with Amil Gaoul and teleports to Calm where the city's wind has returned.