So a while ago I had an idea of including a little bit of Time Travel into my campaign, however, it's incredibly complicated and can have some problems. The idea I had however last night is this:
Time Travel will not be something commonplace, in fact it is only feasible by using a long and forgotten arcane chamber designed specifically for this. The Chamber has a huge obelisk that serves as the time machine. It's pretty straight forward, once you unlock the powers of the obelisk you can travel back to 1 point in the past.
That one point however, is sitting on a sliding rule. What does that mean? It means that the obelisks transports you exactly 1,000 years to the day into the past. So, if this wondrous machine were here, it would allow me to travel to January 11, 1009 AD. And then the next day, I would travel home to January 13, 2009 AD.
So that helps the idea by keeping player from being in two places at once (like traveling back in time five minutes so that there will be two of them). And to keep players from being alien items (like Steel for example) they appear naked like in Terminator. In my Campaign, the chamber has a lot of crumbling skeletons with rusted weapons. When you show up 1,000 years into the past the skeletons are dried year old corpses. (with clothes, armor, and weapons in low repair but not trashed)
Some DMs might want to allow Players to go to the past to change the future. But what I like is that whatever happened has already happened and you cannot change it. I like the idea of Players traveling back in time to stop an evil sorcerer to ascending to evil godhood. And when they find the epic sorcerer and kill him in a battle that leaves the planet shaking they end up releasing his spirit and making him a god. Or if one of them were to marry a woman they would create a family that probably still exists (although it's incredibly unlikely they would find their ancestor). The reason for that is that I don't think that too many people would know where to find their ancestor (or for an Elf who lives about 300 years, his Great Great Grandmother)
My reasoning for the easy cover up for the Grandfather paradox is just the fact that I do not know what my Great Great Grandmother was up to.
What do you think? any loopholes I should address? It's magic, so it doesn't have to make perfect sense. but I want it to be as logical as possible.
I would just like to mention a method of time travel I read about in a novel (forget the name, its by Micheal Swanwick).
Basically the father you go back in time, the easier. In the book it was only feasable for people to travel to the Age of the Dinosaurs, so archeologists were the main people who did it (mind you three separate generations of archeologists together can cause some trouble in avoiding paradox).
So maybe you could have the PCs go back even farther and farther in time.
Now to the main point of the post, I guess there isn't really any glaring problems with this, and to avoid the some paradox problems, just have it so the PCs have "already" gone back in time, so whatever they do it can't alter the timeline, because its what happened anyway.
You could also go with the method they used in Neverwinter Nights were you were transported by an artifact to a specific day.
Another idea is to have the time machine generate a separate instance of the time in question which can be interacted with fully, and used to gather information about ancient temples and the like, but everything you do will only be done in that specific instance. It won't have any effect on your own time.
Sounds interesting. I wonder if an entire Campaign set in modern times could be created around this...