Aang spiritually contacted AvatarKuruk in the realm of Koh when he was in a coma caused by Azula's lightning attack. Kuruk asked him if he had seen a beautiful woman with long brown hair. Aang responded by inquiring about Kuruk's dilemma, at which time Kuruk proceeded to tell him the story of his wife, Ummi. After the tale, Aang realized that during his encounter with Koh, one of the spirit's faces was that of the woman Kuruk had described. Heartened by the knowledge of where his wife was, Kuruk set off to track down Koh once again.
The only way to access Koh's realm is through a spirit gate. The realm is an eerie place inhabited by a wide variety of spirit creatures, including the giant wolf and curly-tailed blue nose. At the center of this realm is a large, gnarled tree with roots that extend into the sky, rather than into the ground. Surrounding it is a large ravine shrouded in dense mist, though the fog is pierced by tall pinnacles of stone.
Deep below the gigantic tree is Koh's lair, formally named the Temple of Koh. Although most local spirits do not dare go near it, an unspecified feature of the cave is prone to luring strangers in. When seeking Koh, one must venture into his lair with great caution, making sure not to show any sign of emotion. Koh attempts to scare his visitors by continually changing faces in the hope that they will express emotion so that he can steal that individual's face.