Timetravel
Time travel can be undertaken by players with the stat as well as by SRs. ICly most factions probably have access to one or two NPC time travelers.
People who travel in time can go to any point in history, they can almost instantly traverse huge distances while doing so, allowing them to arrive on the other side of the world in seconds.
Time travel appears like normal walking, but the world starts to blur as the travelers walk and then jumps back into focus in the new time period.
It is impossible to travel further forwards in time than you have lived through naturally. When you go back in time however much time has passed for you will be the maximum amount of time later you can return. So if you spent a week in the past you could return a week after you left, or a day, but not two weeks.
The timeline is protected by certain causal forces.
Contact with yourself is fatal, even partial removed causual contact can cause large amounts of pain. Most time travelers avoid the last twenty years or so if they can because of the prevelence of communication technology makes contact harder to avoid. Walking through the background in a crowd that's being filmed live and having your other self glance at a tv can be fatal.
The less instant the contact and the less direct the safer it is. A letter that takes a few days to arrive would still hurt but have no risk of death for instance.
It is also impossible to convey information about the future to those in the past. Any attempt to do so will cause you to forget the information just as you're about to impart it. This includes writing things down.
Items that have not yet been invented in the time period traveled to will warp in the process. Those which are highly similar to things found in the past will change to be those items, ones which aren't will just become a mangled, useless mess.
It is possible however to contruct items that do not exist in the past once you are already there, although of course that's rather time consuming and you can't tell or demonstrate to anybody how it's done or how it works.
Archdemons have some ability to damage causality and often attempt to wage their war through influencing or attacking the past.