This massive, full-colour volume is filled with deep resources just for the Delta Green game master.

THE PAST: details on the world and history of Delta Green.
THE UNNATURAL: details on the Cthulhu Mythos, from monsters to hypergeometry to the Great Old Ones, including rules for creating new threats.
THE SCHISM: deep details on the Delta Green organisation itself -- or rather, two different Delta Green groups, not always working to the same ends.
THE OPERA: guidelines for creating scenarios, running campaigns, and customising the setting.
APPENDICES: a ready-to-play scenario, "The Sentinels of Twilight," a Handler-facing glossary, index, recommended media, sample NPCs to use in any game, rules variants, and more.

Further terrors can be found in the companion volume, the silver Ennie Award-winning AGENT'S HANDBOOK, and in the free quickstart rules, the gold Ennie Award-winning NEED TO KNOW.

It may not be possible to ship very heavy items outside of the Mainland UK.
Released: 01 June 2026