They worship a mountain that they refer to as their "dread and terrible lord," kill slaves as sacrifices, drink human blood, and make offerings of their own flesh and limbs.
Laccki is a terrible mole: he lacks anything even vaguely resembling stealth or subtlety, and Dread is suspicious of him from the very moment of his creation.
Laccki is such a terrible mole, in fact, that one suspects his real purpose is not to spy on Dread, but rather to remind Dread that Overmind doesn't fully trust him.