As I understand, they will come into the game as random villages on the map. They will then proceed to scout villages, presumably at random. This is how you find the pieces of the wonder of the world (ww). When you know that you have found the natar you have to attack it to get the piece of the ww. The difficulty is that they will retaliate very strongly when attacked so be prepared, they will not attack until attacked though. At this point merry hell will break loose as the larger alliances start to jockey for both position and control of the ww. Larger alliances will start to inflict large damage to smaller alliances in an attempt to gain power.http://forum.travian.co.uk/showthread.php?t=32185
If you look at the page I have posted it shows the length of time each server has been running. The endgame lasts for about 6 months so we are still fairly safe at the moment.
I have not been through the whole of this process as I started a game towards the end of the last server 1. I learned a lot from the alliance that I was in at the end but it may not be totally accurate.
If you have any other questions I will try to answer them.