Dimensional lesion

A dimensional lesion acted as a portal from one place in space/time to another. Those who travelled through them suffered no ill effects, unlike users of vortex manipulators. Where/when the lesions led to was at random. Lesions might happen when a time-travel-capable vehicle like a TARDIS collided with another craft. If said transport arrived in the location it "bumped" into the other craft some time later, more lesions might be created. They could, however, be closed with an improvised device and detailed knowledge of the event, as the Eleventh Doctor did. (VG: The Gunpowder Plot)