After a few games, I decided to start a new save. I selected the normal difficulty and selected my spawn location: an island surrounded by water. By Deepmun 8, I built a bridge to reach the rest of the map. It is now Deepmun 15 and no monsters have appeared, not even the goblin demanding tribute. This leads me to believe that the town needs to be connected to the terrain to be subjected to raids, as slabs count as a building only.
Steps to reproduce:
- Choose normal difficulty (it probably does not matter if it’s normal or hard) and choose the Ascendancy in the forest.
- Reroll the map until an island is found. Then settle there.
- Build a bridge from the island to the mainland.
Note: This was alpha 21. (probably doesn’t matter)