Grigori Mandate, Heavy Rain Division, Black Water Company, Special Mission Unit.

The name 'Grigori Mandate' both refers to all of the Imperial Guard Regiments that fall under it, as well as the mandate that enabled their founding, issued by Lord Inquisitor Grigori Faust of the Ordo Hereticus. Though he knew fully well that he could requisition any Imperial asset at any time when he needed it, the Inquisitor tired of disbanding them when he no longer needed them, and more importantly, he tired of the delay between when he issued orders and the men needed were under his command.

Though the legislation in the Mandate itself was worded exactly as complex as the Administratum prescribes, it boils down to a simple concept: Grigori's own birth planet, Nox Loctum Prime, was turned into a 'factory' for the Inquisitor's private army, much like most of Cadia's population exists solely to guard the Cadian Gate. Unlike the Cadian Regiments, the Nox Loctum Regiments are much more mobile, required to follow the Inquisitor on his journeys.

The Regiments are divided by speciality in different Divisions, and further divided into Companies and Units as appropriate. The Heavy Rain Division is named after a euphemism Grigori once used to warn a heretical Planetary Governor when the man refused to turn back into the Imperial fold. He warned him to "watch out for heavy rain", referring to the Valkyries, Vendettas and Storm Troopers that were about to make planet fall.

The Black Water Company, Special Mission Unit exemplifies the Heavy Rain Division doctrine of being a airborne rapid response force as their elite warriors, composed almost entirely of veterans and often lead by Inquisitor Grigori Faust himself.