Quantum Probability Flux
A Quantum Probability Flux is an event which occurs in the fabric of the universe that can cause the nature of probability to be altered in a chaotic manner. This can result in unlikely events becoming extremely likely, as well as other events being removed from the likely hood of occurring. This can do everything from changing an individual's birth date to causing entire worlds to cease to exist.
The cause of these events are unknown and may simply be tied to the random nature of the universe.