Inside lives a goblin that feeds on indecision.

Many worlds believe theirs is the only timeline. Even "time travelers" believe in only one real timeline; the others cease to exist when the past changes. Previous timelines become inaccessible through linear time travel, so nothing in their science disproves their theory.

Sufficiently advanced travelers have means beyond these simple "time machines". World Jumpers can identify a parallel time line in infinite-dimensional space and "jump" to it directly. Jumpers typically arrive at a point in space-time equivalent or at least analogous to the point they left. Consequently, jump does not create a cloned timeline, since the jumper is not native to that time line, nor did he move backwards along it.

1. Infinity Unlimited perceives the multiverse as a series of parallels and echoes arranged in "Quantum Levels". According to their theories, manipulating the timeline moves it among Quantum Levels, making it more or less accessible to "homeline". A rival organization from another timeline, called Quantum, holds to similar beliefs. In fact, their flawed method of locating timeline causes timelines to become less or more accessible as new branches appear.
2. The near-godlike Probability Walkers unconsciously shift themselves among actual and potential timelines depending on what they desire. One group called Amberites believe that only their home timeline is "real", and all others are "shadows". Sightings of another group of reality-warping Lords have yet to be confirmed.
3. A civilization of quasi-crustacean fungoid creatures have spread throughout spacetime in multiple universes, including those normally hostile to organic life. These beings are notorious for infiltrating less advanced planets and stripping them of whatever resources they need.