Well in my idea its not time travel it is just various lands at different stages of their timelines. For example there is a world where the phade virus is ravaging the people this land is based on victorian london in the 1900s. Another land if all futureistic but a nano cell invection is creating zombies.

This is what i had in mind you know lands that are easy to reach by normal means but are different enough to be pretty cool on their own...

as far as getting the other books I plan on creating the groups on my own...