The Hrud were once a splendorous race. Concentrated inside one small star system, they never felt the need to travel far. They were not incredibly technologically advanced, but the culture rivalled that of the Eldar, albeit in a more primal and bestial way. They formed strong family units, similar to a clan structure, and flourished. They bred quickly and profusely, and thrived.
Then, disaster struck.
Suddenly, with no warning whatsoever, Warp storms began to tear through the <unnamed> system. Planets disintegrated gradually, with nothing but asteroid and debris fields remaining. The Hrud Elders (A council of elderly Psychics, named Seers) on the systems capital planet decided that the only way to escape this cataclysm was to build an enormous vessel, not unlike a space faring version of the Ark that is occasionally featured in Heretical ancient texts, and set it adrift on the Warp. They had their best engineers attend to the vessel, and within a few weeks it had been constructed. Although it was nothing more than a huge Space Hulk, it was the only chance of survival for the Hrud, and they boarded it in their thousands. The Seers placed upon it psychic wards to protect it from the ravages of the warp, and launched it.
Meanwhile, those Hrud that remained on the planet (the seers, and a handful of warriors and priests, as well as the races criminals) waited for death.
They did not wait for long.
Aboard the new colony ship, there was chaos. Without the Seers to lead them, the Hrud disintegrated into petty infighting. Great battles broke out across the vessel, and many Hrud died. This lasted for 13 long months, until the ship unexpectedly dropped out of the Warp, and directly into realspace in front of an abandoned Imperial hive world. Seeing this as an opportunity for a new life, the eldest of the surviving Hrud guided the ship down using its rudimentary propulsion systems.
The Hrud, glad to see solid earth again, forgot their squabbling and set about disembarking, looting the planet for all they could find, and setting up their homes once more.
It was only after a few weeks that they realised why the planet was abandoned in the first place.
Newly born Hrud began to show worrying deformities. Some were born with extra limbs, some were born particularly large or small, deaf or blind, and all manner of other, more horrific things.
The Hrud, recognizing the signs of Chaos Mutation, fled underground, hoping to save themselves from the Warp Polluted air. They built huge underground hives, and became brilliant diggers. They lived in perpetual darkness, making their eyes extremely sensitive to light, and making them more likely to emerge from their tunnels at night.
However, their digging efforts unveiled more than a new life. For deep within the planet, they found shards of a material as yet unknown to them.
They named it Wyrdstone.
Now, some thousands of years later, they use this Wyrdstone for a variety of things, including weapons and propulsion systems for their craft. They travel the stars as pirates and scavengers, salvaging whatever they can find and adapting it with their own Warp based technology. There are still those amongst them who have the deformities of old, but they are not shunned, instead being used for various purposes. And there are also those amongst them that show psychic power and claim to be the new Seers, but their words fall on deaf ears. The society of the once peaceful and cultured Hrud is gone. Now they are the survivors, the fighters, the pirates
The Nocturnal Warriors of the Hrud.
The Hrud usually carry one of their Warp based weapons. As such they can be armed with any plasma weapon, especially Hrud Fusils. Other than that, they will mostly carry common weapons, and little or no armour. Bolas are a favourite, as are throwing weapons.
A combination of any of the following abilities are recommended- Acrobatic, Ambidextrous, Catfall, Dodge, Lightning Reflexes. Seers will always have a Wyrd ability. Mutated Hrud may exchange some of their statistics (swapping their high initiative with their low strength, for instance, if they are of a huge build), and may also benefit from one or two exotic abilities.
Hrud halve visual awareness distances in bright light, and double them in darkness, due to the long periods of time the race spent underground all those years ago, and even now on the planets it has settled.
A rat ogre, wearing a large robe/cape sculpted from green stuff, should do it, although this may look a little overly muscular (could well be a mutant with exceptional strength). Weapons can be converted from old Tyranid or Skaven weapons. Alternatively, you can scratchbuild everything if you want. (like I did)