After taking a look at the others, I feel it's a bit like this: Graal Delteria is first (taking place thousands of years in the past during the war between good and evil mentioned in Graal the Adventure), next is Graal ol West (taking place in the ruins of the war as people now begin to rebuild civilization out from the dust. The baddies/ monsters have fled far away during this time.), after that its Graal Classic (Takes place not long after the Adventure as it has a lot of the same exact Npcs. The baddies/monsters have returned and invaded Graal.) and then its Graal Era (hundreds of years later, cities were built over the land as society grew more modernized. Due to over Bking, baddies/monsters are now declared extinct.) and finally we arrive in Graal Zone (Technology has advanced to the point of space travel. Alien contact has been made. People now look forward to colonizing other planets).