Caius Thorn is an Adeptus Astartes of the mysterious Stormwatchers, a Space Marine Chapter practically unknown beyond the reaches of the Caligari Sector. Even most Inquisitors doing the Emperor’s work in the region are unaware of their presence in the Sector. The existence of the Stormwatchers has been classified for many reasons, and just partially because they are the militant arm of the Caligari Conclave, deployed only for the most secretive missions.