Haven Zero has multiple parallel timelines, where time travel can only be done on individual ‘threads’ and changes tend to merge and dissipate over time, requiring players to work around these limitations to make lasting impacts.
There are three timelines that are basically ‘normal’, in that they have people in them and a recognizable history: Commonwealth, Legacy and InterAct. Plus there is Zero.
These timelines don’t really work like the standard idea of ‘timelines’.
All of them exist independently, and the way to think of them is ropes with a bunch of threads comprising them. All those threads entangle with each other, and mostly dampen out changes to ‘the average’. And time travel is to, and from, only one thread at a time. And anything you do tends to be overridden by the other threads, and they merge with each other and dissipate and basically, unless you work pretty hard, anything you do is just going to vanish.
The entire campaign will be you working around that to make real changes. To figure out how to make changes stick. Or…just stealing stuff and not worrying about it. Don’t worry about this for now.
You will be living for the campaign on a forth timeline, called Timeline Zero, which has a city/island called Haven Zero, that is a sanctuary for temporal refugees like yourself. A temporal refugee is someone who cannot go back to their thread, and is the reason that Haven Zero was created.
Two common reasons for ending up that way are: a) you found a time machine and ran off, either with someone or not, and now you have diverged too much to return, or b) Someone tried to ‘save your life’ from your normal fated death, but as that is not how time travel works, all that did was create a version of you still alive but without a thread to be in.
Also, most of the stuff I am presenting as things you would want to do is aimed at fixing Legacy, which is ‘us’ with a few changes and the time there ‘currently’ is 2011. (Which has very little bearing on anything, you can be from any point.)
However, past the starting premise, it’s entirely up to you. I think I’ve made all the timelines pretty interesting and worth visiting.
Also, there is a boatload of in-character documents, a lot of it explaining things in-character.