Explore a deep underground facility full of secrets and horrors in the latest Fallout 4 quest modification from the Commonwealth Story Expansion Project.

Background: CSEP's track record before Under The Stars

The Commonwealth Story Expansion Project, or CSEP, is a group of modders known for creating extra quests for Fallout 4. Its earlier work includes projects centered on deadly cults, underground wars, post-apocalyptic detective work, and Brotherhood of Steel drama.

That history matters because Under The Stars is not the group's first attempt at expanding the game's story. While this latest dungeon and quest mod may not appear to be as large an undertaking as some previous releases, CSEP's prior output suggests the project is designed to fit smoothly into the existing Fallout 4 experience.

Development: A new quest follows last month's town addition

Last month, the modders added a whole new town to Fallout 4. After that release, the group put out another entry in its long string of extra quests for the role-playing game.

The latest mission is Under The Stars. It centers on a dungeon delve in the Glowing Sea, where a mysterious bunker has been unearthed. The project is introduced through a teaser trailer titled CSEP Presents - Under The STARS - Dungeon and Quest Mod Teaser Trailer, which can be watched on YouTube.

CSEP describes the mod with the line: "The harsh radioactive winds of the Glowing Sea have uncovered a deep underground facility full of secrets and horrors."

What players do in Under The Stars

The mod tasks players with donning a hazmat suit and traveling to a sunken bunker in the region of post-apocalyptic Boston with the least chill weather.

Inside the facility, players encounter voiced holotapes and puzzles that provide clues about what happened there. The mod also includes new gear intended to reward those who explore whatever lurks inside the bunker.

Spoiler warning: What the screenshots suggest

Spoiler warning: Judging by the screenshots, the underground facility appears to be an Area 51-esque hidey-hole for evidence of aliens and other cryptic oddities.

Latest progress: Fallout Flood and other releases

Under The Stars was created as part of a community-hosted modding jam called Fallout Flood. This particular project was based around the theme of being underground.

Other works that have come out of Fallout Flood so far include another Fallout 4 quest mod called Stranded - The Oasis, a dungeon full of funky rats called the S'Laven, and a new robot enemy that players can wear as a hat.

The modding jam has also produced a New Vegas quest mod about exploring an abandoned NCR railway, which suggests the event has been a productive gathering of modding minds.

Current stage: Requirements and availability

Players who want to try Under The Stars need a copy of Fallout 4 with the Automatron and Vault-Tec Workshop downloadable content.

At this stage, Under The Stars has been released as a Fallout 4 quest mod, and its teaser trailer gives players a first look at the Glowing Sea bunker, the puzzles, the voiced holotapes, and the new gear waiting inside.