Pending GM approval
For obvious reasons of pacing, Avatar: the Last Airbender does not provide in the show itself some kinds of setting information that are important for an RPG. Also, as the total amount of content in the series is limited, it leaves many details of the worldbuilding ambiguous or incomplete. Thus, it's necessary for the worldbuilding of this Avatar RPG to pick up where the canon leaves off in terms of designing the setting and fill in these details. Also, the campaign will depart from the show canon as necessary to accommodate its concept, in which the players' original characters will replace the canonical Team Avatar.
Expanded Worldbuilding
Differences with the Show
Use of Official ''Avatar'' Media
Canonical Characters
For the most part, canonical characters from the show still exist, but their circumstances and the precise unfolding of events differed in such that they did not join Team Avatar. As examples, Toph Beifong presumably remains in Gaoling, winning underground earthbending tournaments. Aang was probably a talented earthbending prodigy who lived a century ago (although we suppose he might have ended up frozen for some other reason.) It is not expected that the party will encounter any canonical character replaced by a player character.