Time Travel

[SlashRunner]

Greetings, Playground

I was recently pondering the idea of homebrewing a Homestuck tabletop RPG (I am aware of the existing one, but I'm not a big fan of 4e/Gamma World and I'm in the mood to make something original). It was all going well and good until I started thinking about how one would handle the time travel that occurs in it. Considering that there are characters who can time travel at a whim (I don't think that's a spoiler), this could pose quite a problem. So, would anyone be willing to help or give any suggestions as to how one would handle a large amount of time travel in an RPG?

EDIT: Also, I was torn between posting this in Homebrew and Roleplaying Games, as this isn't really a piece of homebrew as per say and it seems fitting with many threads I've seen in Roleplaying Games. If this is in the wrong subforum or if it would fit better in Roleplaying Games, could someone let me know so I can request a move?

[Grinner]

Well, you could try setting up a standard timeline comprised of past events, present events, and future events. Then, provide guidelines for determining the effects of a change in the past and its bearing on the future.

Like any good episode of Doctor Who, it's going to get confusing. Fast.

[Roc Ness]

I've actual considered this notion for a while. I've found that, particularly to advantage to PbP games, you can go back and edit your posts "changing the past". :smalltongue:

Of course, to do this successfully, you will need an extra thread devoted to making rolls (so that the rolls don't screw up), and you also need a thread that works as an "alert" to the occurence of time travel, so that people are aware they have to edit or delete some posts to account for this.

[SlashRunner]

I understand that a good deal of it would have to come down to DM fiat, but that's not really the problem I'm thinking of. The main problem is how to handle people from the future popping up in the past. For example (no major spoilers, at least none that I can think of, but spoilered just in case)
Let's say Dave is the Hero of Time, giving him easy access to time traveling powers. Dave is going about on his business when, suddenly, a version of him from the future appears.
How would I handle this? Would the future-him be an NPC? Would the DM decide when future-hims appear and then force the character to travel back in time to validate their existence?

EDIT: Wow...I somehow managed to QUADRUPLE post...

[CarpeGuitarrem]

I've actual considered this notion for a while. I've found that, particularly to advantage to PbP games, you can go back and edit your posts "changing the past". :smalltongue:

Of course, to do this successfully, you will need an extra thread devoted to making rolls (so that the rolls don't screw up), and you also need a thread that works as an "alert" to the occurence of time travel, so that people are aware they have to edit or delete some posts to account for this.
That...is an awesome idea. Have we finally got a genre that is ideally suited to PbP??

This would actually solve the "how do you decide when to bring in 'future me'?" problem, too. You edit "future me" into the story, when "future me" is now "present me". Oh, man. I totally want to try and run something along these lines in Google Docs.

[SlashRunner]

While I do agree that editing past posts is a really cool idea, I'd prefer to not have such an important mechanic be tied to a certain medium of play.

[Mystify]

You need some way of handling paradox.
For general flow of the game, it is best to keep progressing it forward in a linear manner.
As such, incorporating future actions into the storyline the first time through works better. If you have to go back and replay everything whenever somebody goes back in time you will never make any progress forward in the plot.
The mechanic I suggest would be to invoke future involvement at will.
In order to do so, you must create a "Debt" card. This specifies what you must do later to fulfill these events. Specify the level of the character, their status, relevant items, etc. This character can then appear, and act as another character. Anything that happens to them at this time is recorded on the debt card- if future you takes 150 hp of damage, it is recorded. This debt card will then have the recording of every change that happens during their trip back. Items lost, spells used, etc.
You then keep a log of every debt card you accumulate. You must pay back every debt at some point. To do so, you must travel back to the time on the debt card, and possess all of the relevant stats. If the debt card says you had a certain item, you must be sure to bring that item back. If you used spells, you must have those spells available to cast. Etc. You then activate the time travel, and apply every change on the card to your character .You take damage, lose items, etc. based on what happened. This fulfills the debt, and you can discard the debt card.
If anything happens to prevent you from fulfilling your debt cards, bad things happen. If you have a limit on how far back you can travel, that creates a bound on the time you have to pay off the debt card. Failure to pay off a debt card results in paradox. This should be something extremely bad happening. It might be catastrophic to the campaign, you may rewind time to when the debt was incurred, and progress without their involvement, it may just kill the character who has the debt.
Then you must account for potential paradoxes that are not contradictory. For instance, you invoke a future self, who has a rod of wonder. This means you will need to acquire a rod of wonder at some point so you can bring it back, as it is part of the debt card. This future self now gives you the rod of wonder. You eventually repay the debt card ,and go back in time, bringing the rod of wonder. You now have a rod of wonder that exists in the campaign for a time, but was never payed for and has no origin. This is the ontological paradox. There are a few ways you an handle this. The first is to forbid it. If an item is acquired from a future self, then it cannot be used to satisfy the debt card. This is automatic for charged items, as the number of charges on an item given to you would be part of the debt, and if you use it then you aren't fulfilling the debt. Another way would be to give them a "paradox budget", which they obtain through some manner, but that can be spent to allow an item to satisfy its own debt. So the rod of wonder is acquired from the future, and you can spend 12k from the paradox budget to send it back to satisfy its own debt.
For simplicity, you can dictate that involvement in past events can only occur via satisfaction of debt cards. You can only go back in time to someplace you have a debt card for. This represents that the timeline is ultimately immutable, and if it didn't happen the first time then it didn't happen. Practically, this prevents you from having to replay the entire campaign because the player decides to warp back to the start and change something. If you are fine with re-doing everything, you can lift this restriction, but I think it is too problematic.
creation of a debt card can be done anytime, and the resultant person can be anywhere. You can create a debt card for a version of you appearing in the enemies stronghold, armed to the brink with sweet gear and possessing a lot of powerful spells, and then play through their impact there. You will just have to figure out how to satisfy that debt card later, how to get all of that gear and make sure you learn all of those spells, then get into the proper location to go back in time.
There are also some easier shenanigans to pull off. For instance, you have a corridor with a door blocking it. It is opened from the other side. You can create a debt card for somebody appearing on the other side of the door. They then open the door, and go back to the future. You then walk through the door, then go back in time to satisfy the debt.
If the future person takes damage, that is recorded on the debt card. If the future person is said to not die from that, you must be able to survive that much damage in order to satisfy the debt card. Or, you can declare that after x damage, the future person is killed. Then, when you satisfy the card, you must be able to take that much damage ,but will be killed after it. Satisfying that card will mean you die. The past self could cast a resurrection on the future body, which would be part of the debt card, so when you satisfy the card you lose a level due to the resurrection. OR, depending on how you have the mechanic work, the dead body may automatically be shunted back into the future, at which place he may be resurrected as normal. The former method would also allow you to declare that the future version had the cost of the resurrection on him, putting the cost of the ress. on the person satisfying the debt card instead of the past people performing the spell. Or, if a ressurection won't happen, paying off the debt means the character is killed. In order to pay off such a card, all other debts must be paid off.
The ability to travel back in time needs limits. It should have a cost based on how far back you go, so there are limits on how long you can take to pay off your debt. Limits on how frequently you can go back and how long it can take will make it so the player can't just spam future selfs at problems. Invoking a future self to save your bacon should be a last-ditch effort, not the first reflex. How these work depends on how you want the game flow to work, but without limits this easily surpasses casters in power.
The debt cards should be designed to specify the minimum things needed to satisfy it. Gloss over irrelevant details; don't mention them, and don't make them part of the card. You don't need to know how much health the future copy has, only that he needs at least enough to survive the trip(presuming he does survive). You don't need to know every spell he has prepared, only that he has the spells he used. It is generally best to assume he has the same stats as the current version, and make all rolls based on that. If those stats are insufficient, then you can declare that they are higher, but that higher requirement becomes part of the debt. You will then need to have that stat, through whatever means, before satisfying the debt. If your attack bonus is 15, the enemy's AC is 26, and you roll a 10 for the future version to hit the opponent, you can declare that their attack bonus is at least 16, and make that part of the requirements. Then, before you go back, you will need to be a higher level, or have bless cast on you, or some other means of raising your attack bonus.
But the general goal is to make the debt card as non-specific as possible, so it is as easy to satisfy as possible.

[Sodalite]

That's is quite comprehensive. An idea for limiting the invocation of future-selves might be some standardized test, a simplified representation of what challenges your future-self might have in trying to reach your time, plus some randomness to account things beyond your future-self's control.

[Mystify]

That's is quite comprehensive. An idea for limiting the invocation of future-selves might be some standardized test, a simplified representation of what challenges your future-self might have in trying to reach your time, plus some randomness to account things beyond your future-self's control.

The challenge of going back in time to satisfy the requirements should be left up to the player. They have to make sure that they only invoke future selfs that they are reasonably certain they can satisfy. The DM should help the character satisfy their needs, within reason. For instance, they could find an item as loot that the party got from a future copy. This shouldn't be made into a guaranteed thing, but helping the player make a cohesive timeline would make things run smoother. This doesn't mean give the players the +10 sword of power as random loot because a character invoked it, but if he pulls out a potion of cure light wounds, you can toss it in a loot pile.

On idea for limiting their travel is making it into a psionic power. You can augment the power by so many points to travel back different time spans. The player can't invoke more future copies than he could manage to create by spending points. If he does, he won't be able to satisfy his debt, and bad things happen.

Considering its MSPA based, not satisfying your debts could be tantamount to creating a doomed timeline, which would mean that everyone dies. Campaign-wise, you might have to rewind to a stable point. But it should be something the player is trying to avoid at all costs.

The other advantage of the debt-card system is that it replicates the feeling of running around and making sure that everything that happened happens. Dave made a statement to that effect at one point. He was just going through the motions to make sure everything worked out. Sitting there with a handful of debt cards would feel like that.

[SlashRunner]

*snip*
That's... that's great, actually! Thank you! I wasn't expecting anything nearly as well thought-out! That actually sounds like a really good basis for the system, and unless I have some kind of stroke of inspiration, it's probably what I'll end up using. Thanks a lot.

[Absol197]

That's... that's great, actually! Thank you! I wasn't expecting anything nearly as well thought-out! That actually sounds like a really good basis for the system, and unless I have some kind of stroke of inspiration, it's probably what I'll end up using. Thanks a lot.

And that system is only necessary when time travel involves interacting with your past selves, or other events the detail of which the party will know when it first happens.

You can also plan parts of the campaign where events happen in the distant past that set up the beeginning point of the campaign, as well as make passing references to events (if in a modern setting, through TV news broadcasts, or in a standard D&D setting, through gossip and/or heralds) that give general facts but no details, and later have the PCs fulfill those events. They wouldn't need "debt cards," because no details were given in the first place, so nothing needs to be defined beforehand.

[Mystify]

That's... that's great, actually! Thank you! I wasn't expecting anything nearly as well thought-out! That actually sounds like a really good basis for the system, and unless I have some kind of stroke of inspiration, it's probably what I'll end up using. Thanks a lot.

Glad to help. Time travel theories is something of a hobby of mine.