"This place looks like it was flooded a long time ago. The highest lands have formed a set of islands connected by natural bridges. It is a region rich in resources, but is a complicated location to build a large colony. In addition, there are ancient doomed villages on several of the islands and many infected that have concentrated in the high ground after the flood. Build a large colony and kill all the infected in the region as well as the swarms that approach the colony."
South-west is the recommended direction for early expansion.
Due to unknown reason (probably a bug), around 60~ infected will be destroyed right after starting this mission, which gives you extra starting gold if you have Corpse Recycling and/or Black Market technologies.