When a massive, mysterious structure suddenly rises from the ground, the government sends a team to investigate. You have been selected to join an elite group of underground explorers know as "Undernauts" employed by the Cassandra Company. Unfortunately, you are not the only one searching the caverns. Terrifying monsters lurk in the shadows. Others hunt for resources. Large numbers of people are missing. Dangerous criminals with mysterious powers are out to thwart your efforts and eliminate your team. The ultimate test for survival is found in the labyrinth. Can you be victorious and rise above the shadows?