There is also the story archetype, where the quest is not really to defeat the enemy, but to get the McGuffin. In such a story, you could put the zombies in as obstacle, to prevent prevent the pcs from getting it without proper and lengthy preperations.
In such a campain you likely have enemies (or "enemies" like the apathy of the other survivors), but they might still be only single adventure enemies, while what keeps the campain together is the McGuffin.
Something that goes a little bit in that direction are the Rebuild and Rebuild 2 online games.
One mans groundfloor is an other mans earthmissle @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Johannes Trimmel @@@@@@@@@@@@@@@@ _______________________________________________ GurpsNet-L mailing list <[email protected]> http://mail.sjgames.com/mailman/listinfo/gurpsnet-l
