“The Guru” is the penultimate episode of Avatar: The Last Airbender Book 2, and it introduces Guru Pathik (Brian George) as Aang’s (Zachary Tyler Eisen) spiritual guide. After receiving an invitation via Appa, Aang visits the Eastern Air Temple hoping to learn how he can master the Avatar state. Instead, he gets an elaborate lesson on the nature of spiritual energy and its relationship to the chakras. Nearly two decades after its original release, “The Guru” feels even more relevant than ever before.