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. To where/when the lesions led was at random. Such occurences might happen when a time travel capable vehicle such as a TARDIS collided with another craft. If said transport arrived in the location it "bumped" into the other craft some time later, more lesions will/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)