Temporal inertia
From Tardis Wiki, the free Doctor Who reference
Temporal inertia was an aspect of time travel that related to the creation of alternate timelines. A great amount of power was required to overcome the temporal inertia that came with adjusting the timeflow, but it was possible. Beings that could do so included the Chronovores and the Guardians. Even Rassilon, the Doctor, and the Master could possess the know-how. (PROSE: Blood Heat)
