Omashu and Ba Sing Se have been vipers' nests of mutual espionage for years. The west already hosts Fire colonies, including Yu Dao since 37 BG. Southern floods earlier in the era pushed refugees toward the Outer Wall. Kyoshi's legal and cultural shadow is everywhere. The 12 BG queen of Omashu is unnamed in canon; this world uses Queen Meishou [Original].
OMASHU
The city is built in a mountain, famous for its delivery chutes. Queen Meishou holds the throne terrace above the chutes and will risk a crisis to humiliate Yuanli. She is sharp, competitive, and not a villain by default — she is a second Earth capital that refuses to be a province. Captain Sern holds the Great Gates and the outer earth-wall post. Foreman Dak runs the Delivery Chute Hub, Mid-Ring Depot, and swears the last three stoppages were not accidents. Smith Heng works Heng's Chute-Iron on the depot side street; his apprentice has gone missing after a "Ba Sing Se order." Master Cho keeps The White Teacup parlor — front room for tea, back room for Pai Sho that is sometimes more than a game. Grand Lotus Amara uses that back room when she is in the city.
Questline: Chute and Dagger. The delivery system fails again. The queen wants proof of Ba Sing Se sabotage. Dak, Heng, Sern, and Cho all have pieces. A party can be chute workers, guards, or outsiders hired to "make the city look competent." Omashu will out-spy, out-build, and out-brag Ba Sing Se without open war if it can. If it cannot, Meishou may accept a little fire on the western border as long as it embarrasses the Earth King more than it burns her gates.
YU DAO AND THE COLONIES
Yu Dao is a mixed Fire-Earth city in the western Earth Kingdom, a colony that has existed for a generation. Roku forbade further expansion after the crisis that created it. Roku is dead. Governor Ryozen works the upper terrace of the Governor's Residence and has Mandate correspondence about "future military use." Master Bohai, of the Brick Lotus resistance, bakes in the Old Earth Quarter basement and will deal with Omashu or the White Lotus, not the Dai Li if he can help it. Ferryman Wudao runs the public slip and can stall a patrol. Dock worker Sarn works the smelter quay; his sister was "reassigned" to a locked warehouse. This is the powder keg of year one. See the dedicated Yu Dao lore page.
OTHER WESTERN AND SOUTHERN PLACES
Chenbao and the Northern Passage remain a raw border after the earlier tsunami-and-tax crisis. Governor Pei sits in the tax hall overlooking the Passage and stamps cargo that should not move. Polar ships and Earth batteries stare at each other. A regional war here would give Sozin cover.
Broken Cliff Academy is the home of Sud, a canon earthbending master, now elderly. Practice terrace and stone garden. Letters from Roku are under a paving stone — unease about Sozin, in Roku's hand. Sud will still teach a serious student, and he will not travel quickly.
Kyoshi Island is its own culture: Main Village Gate (Michi), Village Square dojo and Unagi Shrine hall (Headwoman Oyuki), harbor watched by the Unagi. Fire sails have been sighted in the eastern sea. Oyuki has an old White Lotus tile she does not advertise. The Kyoshi Warriors are typically nonbenders in makeup, iron fans, and discipline.
Si Wong Desert: dune-market tents, sand-sails, and Wan Shi Tong's Library under the sand. Krik the beetle-headed merchant sells Maps and Beetle-Glass. Dart, a knowledge seeker, meets visitors at the entrance descent. Wan Shi Tong sits in the central nest and already dislikes war tourists. He has material on comet-cycles. Visitors must add knowledge, not only take it.
Senlin Village's sacred forest already has a forest spirit, Hei Bai. Logging and "resource" teams have started measuring the trees. If the forest is harmed, the spirit will not stay a statue in a shrine.
Hualin flood ruins are mostly empty if Joru has already taken the Wall offer. Gaoling foothills and mining roads are caravan country and a place to meet Sud's visitors.
Play any of these as a full campaign home. The comet clock still ticks if the party never sees the Caldera.