Not Imperial Guard, but personal retainers, hereditary soldiers of one specific dynasty.
Do not mistake their Askarii status for any lack of professionalism. These men, the sons and grandsons, cousins and so for many generations, have honed their craft to a fine level.
And they are armed and equipped to be the envy of all the 'guard but the Kasarkin. These men are also schooled in multi layering their thoughts to provide an initial level of protection against psykers.
The current scion of the Dynastic house they serve just happens to be a member of the Ordo Malleous.
It always helps when the boss enthusiastically leads from the front. It gives them a sense of confidence as well as purpose.
And their leader, the Inquisitor's tool, is also a formidable commander in his own right.
All of the brushwork here was done by Pirate Viking Painting.
