Today’s guest article is by Chris Kentlea of Ennead Games, designer of kits and guides to help players and GMs alike. Thanks, Chris!

Time travel, forward and backwards, is a subject that can cause many problems for GMs and players alike.

The main problem that most people are aware of is the so-called “Grandfather Paradox.” In case you don’t know it, it runs like this:

  • You travel back in time
  • Meet your paternal grandfather (or even your direct parents or another ancestor) and, by accident, kill him before your father is born
  • As your father no longer exists, neither do you
  • As you don’t exist, you can’t go back and cause your Gramps’ death, which means you do live, so you do go back, so he dies, so you don’t exist…

This can cause people to go cross eyed. There are many ways around this problem — the movie Back to the Future perfectly illustrates what can happen when time is changed.

Let’s assume you found a way to solve the paradox and that time can be changed if you travel through it in ways you were not meant to. The temporal paradox is not the only issue you may have to deal with. There are other, often overlooked dangers of time travel include (but not limited to) the following — the key ingredient in all of them being that they make games interesting.


When you materialise at your temporal destination, you have a chance of there being something already there. The method of time travel may replace what is at the destination point with the traveler. If you have the wrong temporal/spatial co-ordinates you may materialise inside a mountain, at the bottom of the ocean, or even inside the planet! Or the tree that would inspire a nation to rise up against its oppressors might be knocked down on arrival.

Technological & Economical

For many people, the biggest lure of time travel is acquiring knowledge. This can range from seeing the birth of a famous figure in your world’s history or finding out next week’s Mega-Lotto numbers with triple rollover. This at first glance is the safest method of time travel. You are not moving, you not going to squash a bug in the past that prevents your species from evolving, and you negate the risk of the grandfather paradox.

The major issue with looking into the past is that sometimes the information you discover is not what the history books record. Your famous leader might have be born normally and not under an eclipse like the legends tell. The slayer of the mighty beast may have been in fact been their servant and they took the credit and fame that went along with it.

Looking into the future, though, is actually much more dangerous than it first appears. Let’s assume time in your world can be changed. What happens if, upon looking through the time window, you spy your own death as you go to buy a lotto ticket?

Social & Linguistic Problems

Language and social customs change over time. A word that means one thing now may have had a different meaning 100 years ago and will mean something else in another 100 years’ time. Not know the correct terms and customs for the time period can at best cause embarrassment or confusion. At worst you commit a faux pas or insult an important person by accidently making a comparison between their mother and a garden implement.


Everything in the multiverse moves. The planet moves around its parent star. The star moves in the galaxy it resides within. The galaxy moves away from other galaxies. It is even suspected that the universe moves. Which is why making sure that your destination is where you think it is, or having some way of compensating for this movement, is so critical when traveling through time.

Diseases, Microbes, and Bacteria

In many ways this is the most overlooked and most dangerous aspect of time travel (after the risk of possible paradox). The destination point (future or past) may have diseases, microbes, and bacteria you don’t have immunity to. Traveling into the past (or returning from the future) runs the risk of introducing a disease or microbe into a time period that doesn’t have the resources to handle it.

Picture this, you take a short expedition to the future and take every precaution you can think of. Sadly a small microbe hitches a ride back with you. Over the years it had developed immunities to many of the most powerful cures. Congratulations: You’ve just introduced a super-virus into a population that can’t handle it.

Going into the past can cause the same problem, taking along microbes that wipe out a developing settlement or creature that is essential for a major hero to be born and kill the mega-demon from the 12th plane of the abyss. A rigorous form of quarantine and cleaning, before and after the time jump is highly recommended.

Hopefully these considerations have given you some ideas for incorporating time travel — and its attendant dangers — into your own campaigns. If you’ve used time travel in a game, I hope you’ll share your experiences in the comments.

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12 Responses to The Trouble with Time Travel

  1. The Spatial concern is an odd one, as most fantasy campaign settings I’ve seen are described as geocentric. This actually removes a lot of the spatial concern, as the earth isn’t in motion.

    Anyway, there’s a bunch of time travel in the current campaign I’m running, but the PCs aren’t privy to it, yet. It’s mostly handled by powerful magic (like, creation-level magic) so many of the attendant dangers with travel itself aren’t an issue. It also has some aspects of hopping between dimensions or universes, but that’s only because the current time travelers are from another dimension… sorta.

    The main problem the most prolific time traveler has in the campaign is insanity, or seeming insanity. Trying to keep track of where and when he is, what he’s currently doing, whether he’s met this person before, and so on has left him being considered extremely paranoid and a little bit mad.

    As for other issues, well, that’s where our crazy time traveler steps in. His primary goal in time travel is preventing the end of the universe. To that end, he repairs times and places that are broken, whether due to time travel, dimension hopping, or whatever. His current goal is to kill a god in the players’ time, and by doing so delay the end and possibly repair some of the universe. Between him and a few of his allies, diseases and monsters who make it through don’t tend to significantly effect changes in the timeline.

  2. A valid point Svafa – but the other issues would still be valid (plus not all fantasy worlds are going to be geocentric)

    Your comment about the insanity from time traveling is a good one – IIRC there was a episode of the Outer Limits where someone was changing time but had the memories of each timeline – the orginal prime one plus each one they had altered – It had the same effect as you described – For me though i put this in the same bracket as the “Grandfather Paradox” (as it could be a manifistation of said paradox) but can see why you liked using it :-)

  3. As Captain Janeway said, “It helps if you just don’t worry about it.”

  4. Great article, Chris. Was the spacial problem at all inspired by my article @ SciFi Ideas? 😉

  5. One mistake that I once made when GMing was surprising the players with the secret identity of a key villain. As it turned out, one of the characters was knocked out of the time stream by a powerful demon, driven somewhat mad and hardened by spending decades worth of time in chaos and then being deposited several months before the campaign began. He had then been working prevent them from their goal so that he could save the party from his fate. In the end, the party hard to fight and defeat a higher level version of that party member in order to complete their quest AND avoid being tossed into the temporal chaos.

    It was twisty and interesting and somewhat convoluted, like all good time travel. All of the players loved it except the one whose character I had turned into a villain. He felt like I had violated his character by taking control of him without permission, even though it was a future version of his character that never came to be. In the end, he felt hurt, I felt bad, and it strained the entire campaign. I recommend staying away from any time travel that would involve the PCs encountering and interacting with future versions of themselves…

    • One way around that you could try is to say/reveal the villan was from a possible/probable future or parallel universe. Then i would be those characters but not the PCs…if that makes sense – plus gives them a chance to avoid fate and gives you a get out as simply knowing their fate could change it

  6. Great article! I enjoyed the disease and microbe–it worked great for Connie Willis’s Doomsday books. Social and Linguistic is interesting; in The Cross Time Engineer, an important point is the slow change of Polish, especially in contrast to English.

    Technological was driven home to me by reading The Most Powerful Idea in the World. I’ve long enjoyed thought experiments about going back and disrupting the past with cool future tech, like A Connecticut Yankee, or similar. (Or like the one guy in every junior high D&D group tries to ‘discover’ gunpowder.) When I saw how many people interacted to make a steam engine really work, then work well enough to be useful out of a mine… well, I suspect that even with blueprints, I won’t be bringing the Industrial Revolution to 500 AD.

    • thank you :-) I’m of the view that if the players put enough effort into it, then devloping gunpowder etc should be possible..of course there will be (explosive) mistakes along the way and ..oh look the local warlord has caught wind of what is going on and decides to pay a visit

  7. An excellent resource for Time Travel games is “The Time Traveler’s Cpmpanion from Cubicle 7, written for their Doctor Who series. It has some very good chapters discussing paradoxes, problems, fixed points, repeated revisiting of same time zones, etc.

    It is Doctor Who centric, but the general comments and ideas are pretty generic. The PDF is pretty inexpensive, so my suggestion would be that if you have a serious interest in Time Travel, or if you have a mild interest in it, but also a mild interest in Doctor Who, that would be good enough to make this a worthwhile purchase.

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