N0-1_H3r3 said:
A Dark Heresy game has its heroes, but they are ordinary men and women made extraordinary by brutal circumstance and grim necessity, to wage a war unseen by the masses, forced to cast aside innocence and blissful ignorance to fight enemies that shouldn't exist and strive towards victories nobody will ever know about.
Basically, it's an infinitely more playable version of CoC.
In CoC you find out about the horrible truth and then when you confront it, it kills you all and you gen up another character.
In DH you find out the horrible truth and then when you confront it, you at least have the illusion of having a fighting chance against it, to the point where it's at least worth picking up the dice and trying. And if the worst comes to the worst you still get to go on a number of adventures equal to your Fate Points before having to gen up a new character!