One World is a twist that featured in Survivor: Ardennes. It is a twist to the pre-merge game of a season, and it initiates a Tribe Switch every two Tribal Councils/eliminations to keep the players rotating round tribes and having to fight to stay alive. The name "One World" comes from the creator SuitMan13.
Every two Tribal Councils (or eliminations if it is a Double Tribal Council), everyone will automatically switch tribes by random draw, changing the game up with each switch. The castaways have to make sure they are fully integrated with proper alliances in the game, or they could find themselves drawing the short straw and getting booted, when they end up on a tribe with people they aren't aligned with. That is why it is vital in this scenario that the castaways cover all bases. The twist finishes at the merge, when the castaways dissolve into one tribe.