Time Travel in RPGs

Time travel stories: extremely difficult to do right at the best of times, practically impossible when you have to deal with the random element of the players standing in your way.

How do you do it right?

1) Have good players. Lolsorandums and morons will ruin even the best premise.

2) Use a multiverse model so that paradoxes are easily dealt with. i.e if you go back in time and kill your grandfather, you don't disappear because a new timeline branches off from that point, and you exist in it as an element from another one.

3) Alternatively do a pulp/soft sci-fi version that either has bullshit timeline physics (like S;G), or is a single timeline complete where you handwave away any chaos theory effects and trust your players not to derp away their own characters' existences.

The usual reasons for time travel in adventures are:

>prevent something bad happening by altering the past
>gain knowledge from the past to use in the future, without altering the past
>accidental time travel, resulting in a struggle to return to the present
>some kind of sentimental reason like meeting the father you never knew because he died before you were born (probably not compelling in a TTRPG though)

...

This is something I've given consideration, but never put into practice.

First, I assume that you want a story actually "about" time travel. That's not the only time travel story you can do: you can also do stories about very distant eras, basically exotic locales or show pieces (Doctor Who does this a lot), in which case something has to be history-making to even risk paradox.

If you do actually want a story "about" the possibilities and paradoxes of time travel, you have to decide how "realistic" (logical) you want to be about it. More paradoxical forms of travel make room for more types of stories, but may strain player's belied, and are open to abuse by really clever players. In order from least to most paradoxical:
0. Impossible
1. Realistic
2. Roughly consistent
3. Mutable with stationary points
4. branching
5. bubbles of time
6. narrative time

1. Realistic: nothing moves in space time. Paradoxes are avoided: you will never succeed in killing your own grandfather, or even a young Hitler. You will not be able to pick yourself up by your bootstraps and "invent" something no one else ever thought of by waiting for your future self to send the plans back in a time machine (because then how did he get it?). You will never own an impossible object that is immune to entropy (the pocket watch your future self gave you... that he got in his past from his future self... who is him. Wait, who made the watch again?)

This doesn't mean that you can't have the flexibility to tell stories: maybe your players don't know and must discover the rules. Maybe they put enough time between points of interest that nothing they do in Camelot can realistically affect what happens in Chicago 2340 AD. Maybe they "change" history by proving that history as they know it is bunk. But it does mean if they go off the rails, there's something that goes wrong and prevents them from killing Hitler/saving Lincoln/etc. No matter how many times they try. That's a big burden for Fate (you).

Realistic time travel has a lot of opportunities for feedback loops that force you to either admit a paradox (bad for believability/consistent player expectations), or to force things to turn out the way they already turned out (bad for player agency).

2. Roughly consistent is sort of fudging. Things are pre-determined, but the players and exact dates may change. Stop Hilter in '35, and you have to deal with the same Nazi's under Kornfleish in '63 instead. Honestly, this is mostly a sign the author wanted a sequel, reason be damned. (Looking at you, Terminator)

3. Mutable stationary points carries this further: history is a collection of big moments that will always turn out roughly the same way. All the small stuff in between is up for negotiation. (Armstrong will always walk on the moon. Whether he eats cornflakes or fruit loops for breakfast that day is mutable.) Again, Doctor Who uses this.

I was always a fan of how Gargoyles did time travel, where you couldn't change time, but there were usually enough loopholes that you could do something with it.

>Archmage travels back in time, gets a bunch of overpowered epic artifacts to boost his power, then sends him back in time to do the same thing.
>Xanatos is a self-made millionaire who went back in time, sent himself something to get his fortune started, followed by a letter later telling him to go back in time.
>People think Goliath killed someone in the past, so he goes back to make sure he doesn't die. Events contrive to stop him from not getting killed in the past, so Goliath gets around it by bringing him to the present, making Goliath responsible for him disappearing suddenly.

Branching universes/alternate realities fix the problem with paradoxes: any time there's a paradox, what _really_ happened is that the timeline split in two, BOTH ways occurred in their separate universes, and the time travel was people from one "original" universe interacting with the other, "altered" universe's past. marvel comics uses this a lot. Again, it's best if you only split timelines for big events (Armstrong). not little ones (his cereal choice), or you'll have infinitely many but mostly tediously identical realities.

>realistic time travel

Do what FF XIII-2 did, don't give a shit about the nitty gritty specifics and have fun with it. Also what said. Multiverse solves a lot of headaches.

5. bubbles of time is something I wouldn't have thought of, because it throws logical straight out the window. Apparently the Flash falls into this camp. Once you change history, you really change history, like recording over an old VHS with new data. But if anything was away from that time at the moment, it becomes stranded and gets to stick around.

So you can clone yourself by getting your future self to come over for beer, then wipe his timeline (stranding him) by calling his slightly earlier self over for beer, and so on until you have arbitrarily many clones. Or you could Rob Fort Knox infinitely many times. Or whatever.

Finally, we have to accept the end-all/be-all of time travel models; narrative time. There is a privileged version of time that exists in the mind of the reader/viewer/player. Your characters timelines may get over-written, invalidated characters may get to stick around after their past never happens because we've already met them, and all sorts of weird shit that makes no sense in real life... but is easy to miss because it makes sense to a privileged observer who's not paying that much attention. You can do some fun stories with this, but if you're not careful the illusion collapses in a fit of arguments about what actually happened five sessions ago, and how after a little thought it makes no sense.