A world with only lords and masters feels empty. Thirty named everyday NPCs exist so that streets have voices, prices, rumors, and side quests. Use them. Put them at the sub-locations on their sheets. Let a party eat before they storm anything.
FIRE STREETS
Nara Jin sells fire flakes at Red Tongue Flakes and saw manacles under rice. Uncle Hwan sells late noodles and is missing a pot. Madam Sora keeps The Ash Lantern and two witnesses in an attic. Smith Togaru at The Warm Hammer refused a quiet chop and is losing coal. Ferryman Batsu runs public hops and may have carried Rina. Dockhand Reki marked the incense crate and hid a tally-stick in a mooring post. Private Sen stands the outer post of the Main Caldera Gate and saw Viro hide a log. Ko the Tiles plays Pai Sho at The Scented Coal window and sells talk to more than one employer. These people are how the Island Witnesses quest stays human.
EARTH STREETS
Old Gan sells cabbages in the Lower Ring (original to 12 BG, not the later cameo). Mei-Lin cooks Two-Bowl Noodles and has a missing supplier. Auntie Pao keeps The Crooked Cart and a back room that has seen Dai Li coaches. Auntie Wen sells broth and hears everything. Corporal Min looks the other way for one unpapered child. Yun the Letter-Carrier walks Silver Lane with a steamed-open letter and an Omashu loyalty. Smith Heng's apprentice is missing after a "Ba Sing Se order." Ferryman Wudao can stall a Yu Dao patrol. Dock worker Sarn's sister was reassigned to a locked warehouse. Master Cho serves tea in the front of The White Teacup and more than tea in the back.
WATER STREETS
Auntie Niri's Warm Prune Pot has a lid-note for Envoy Sana. Pakak has forged stamps in his gossip if not in his ledger. Iqaluk has a sick guest at The Frozen Lantern. Taktuq can carry a verbal warning. Silla has hidden a crate on the Wolf Cove cargo dock. Guard Atuq has turned away an unannounced audience. Old Tukka will test a stranger with a Pai Sho tile. Boatwright Rinuk can tell a war keel from a hunting keel. These stalls are the Passage and the Conclave at ground level.
AIR TEMPLE FEET
Paljor's Orange Basket noticed an incense binge. Mother Tashi's Bison Bell can keep a spy busy or a child hidden. Cook Jigme packs extra pies when the courtyard is too quiet. Saffron Wei needs an escort off a mine road. "Brother" Fen is the reason a kind smile is a threat; his stole-list is Mandate work. Padma's cliff lift is how a non-flyer leaves the Western Temple alive and unseen. Pathik, at thirty-eight, cooking lentils, is everyday and extraordinary at once.
HOW TO RUN THEM
Give each a greeting, a price, a rumor, and a problem. Do not instantly martyr them to prove the Mandate is cruel, and do not make them unkillable. If the clock advances, a stall can close, a ferry can be "inspected," a letter can fail to arrive. Nonbender PCs should get hooks of the same quality as benders: Rina's flight, Fen's stole-list, Viro's gate log, Bohai's bakery, Niri's soup-lid note, Gan's crushed cart. A wall of flame is not an argument in a tea house.