Unstable timelines are alternate timelines that cannot exist on their own and are undergoing collapse. These fictional timelines may have been created due to a paradox during time travel, a laboratory experiment gone wrong, or multiverse shenanigans. Often these are post-apocalyptic settings and strange temporal events may be occurring. The people and factions of these worlds may be resigned to their fate, may be working to save their timeline, may not even know that their existence is collapsing, or may be attempting to flee into a main timeline.