By the cycle, when a Fire Avatar dies, the next Avatar is born to the Air Nomads. Roku has just died. A child has just taken a first breath in one of the four temples, or in a family tied to them. This campaign does not decide which child. Do not auto-fill Aang, Appa, or the later biography of the last airbender.
THREE WAYS TO PLAY THE SLOT
Option A — NPC infant. The party hears of a birth, a test, or a kidnapping. They play as guardians, hunters, or rivals. Monk Norbu at the Southern testing courtyard has already not written a name down. That may or may not be this child. The table decides.
Option B — Player Avatar with a time-skip. Start at the eruption, then use Downtime Mode to jump to age 8-16 at a temple. The missing years can be played in glimpses: a test, a Fire envoy, a bison flight, a dream of a volcano.
Option C — Mid-campaign reveal. A player Air Nomad student is identified after signs, a past-life vision, or a failed Fire Nation census.
LEARNING ORDER
After a Fire Avatar, the cycle of training is Air (native), then Water, then Earth, then Fire. This is the opposite of the last life, and it matters politically: the new Avatar is not a Fire National. Teachers who can help: Gyatso and other elders (air); Taqukaq, Northern or Southern masters, even swamp teachers (water); Sud or other earth masters; Fire Sages or dangerous Fire tutors (fire). Sozin would love to be that last teacher. That would be a trap and a story.
AVATAR STATE
@Avatar State is a last resort at low tier. It empowers the elements you know. It can also let a past life take your body, wreck the area, or drop you like a stone. Roku, as a young man, nearly destroyed the Crescent Island temple forcing the State; Kaja had to pull him out. The new Avatar should fear it a little. Controlled use is a high-tier feature (Fully Realized and Legend). Energybending is almost lost and is not granted by this path automatically.
PAST LIVES
@Past-Life Guidance, once per long rest, may call:
Roku — immediate, grieving, urgent, furious at himself for sparing Sozin, kind to those still willing to stop a war. He did not see the child's face clearly as he died.
Kyoshi — uncompromising, political, long-lived, founder of the Dai Li and of Kyoshi Island. She will tell you to finish what justice requires. She may not be gentle about means.
Kuruk — haunted by Koh and by neglected duties. A warning about spirits and about doing nothing.
Yangchen — air, duty over attachment, a hard standard for an Air Nomad child.
Wan and earlier lives are distant and rare.
POLITICS
The Avatar is a political object. Temples, the White Lotus, Sozin, the Dai Li, and the Crimson Mandate will all move if the identity leaks. Gyatso will lie about a test. Yeshe will hide a child without telling the other temples. Hesun wants the Avatar owned or gone. Amara is already assembling a four-nation hiding route for a child not yet named. Pathik, at thirty-eight, has the first edges of a vision that he will one day help an Avatar — the face is not fixed.
If no PC is the Avatar, still run the world's search. The empty slot is the engine of the decade.