This is a simple map, where everything is pre-built and setup from the start.
However, because you have been slack in your comfort of the region, the God's have decided to teach you a lesson.
So as soon as the map starts, bandits destroy nearly all of what you have, forcing you to start over from scratch and rebuild your castle area.
This is designed more like a free-build, because that's the only real 'event'. You should be able to press F1 to trigger other invasions, and see how your handy work holds up against more attacks.
The freebuild version allows you to hit F1 to trigger invasions to test how well you've recovered. The other version was an Invasion map type, which doesn't allow you to control the manual invasions.
This version of the map also fixes a few minor irritations, like not being able to place things in the corners of the walls of the main castle area, and the waterfall at the bottom of the stairs looks a lot better.