The Chassago Homeworld

This world is the ancient homeworld of the serpentine Chassago, one of the founding members of the First League. The vast majority of their cities were located underground and … is riddled with tunnel networks, of which most have collapsed in the two million years since the Chassago went extinct. Probes from the … have identified the probable locations of several subterranean cities.

The command below will trigger the "The Chassago Homeworld" event in Stellaris:

When this event fires, you can choose between the following option:

• Curious.
  • Start special project: Chassago Homeworld