The Threshold Trilogy is a series of three gamebooks in the genre of cosmic horror:
The Thirteenth Vessel
Geometry of the Abyss
Unsound Methods
The Thirteenth Vessel, the first Uncanny Agency Gamebook, is planned for release in June 2026. It is written by Sean Cooper and illustrated by Leigh Chalker.
The time is now. The world is as we know it… mostly. The difference is that you and your colleagues know something that most people don’t; that our universe is under constant threat from indescribable horrors in another dimension. These unknown terrors are malevolent and powerful, determined to transform our world into a gruesome hellscape.
You work for a secret government department dedicated to protecting the world from paranormal phenomena intent on invading our reality. To the world it’s known as OTS. It stands for Office of Threshold Security, but all anyone outside the department knows is that it’s something to do with very high level security.
You’re a Field Agent. The OTS also has researchers and analysts, anthropologists, and all kinds of scientists, but you are the “boots on the ground.” You investigate and respond to all kinds of uncanny phenomena. You and your fellow OTS operatives are the first and last line of defense against demons from the outer unknown.
Uncanny Agency Gamebooks 