So, I'm going to be starting a Black Crusade game fairly soon, and I want it to be political intrigue. The premise is that a Black Crusade "liberated" a hive world and has since left to attack other Imperial planets, and now the denizens must work to restructure the government. Any imput and suggestions would be great.

Under such conditions then it sounds like you might want to be wary of assassination attempts against the corrupt ruling classes. It is not unknown for the Ordo Hereticus to want to simply snipe them out. We are likely not talking vindicare assassins, probably a man with a gun. One world is probably not enough to warrant a perfectionist like that.

Since you mentioned political intrigue you'll also have noble houses fighting for control over the planet, using any and all means at their disposal. No doubt the players may find it difficult to either play all the houses against each other or eventually be forced to pick a side, as a potent asset cannot stay neutral forever without arousing suspicion as to their true loyalties.

Meanwhile you might have remnants of the original crusade left behind, perhaps a warband from whoever liberated it to remain either as a passive force or one which broke away and is taking to looting, pillaging and capitalising on the benefits of a world now ripe for the harvest. Alternatively being undefended without Imperial assets or a warband guarding it, other factions or groups may see an opportunity to come in and try to steal it since clearly this warlord who had it last didn't stay and cement their claim!

Those are a few ideas off the bat.

And great ones at that.

You could also add in some more mundane problems.

- A stray orbit to surface torpedo which didn't detonate, and is currently missing.

Who took it? what will they use it for? is it even still working?

Or, said torpedo could be lodged inside the hive's main reactor.

- When the crusade arrived, the food supply was tainted by the presence of daemons (daemonic incursion).

As a result some of the lower caste (and several of the noble houses - in secret) have taken to cannibalism. Several important people have already gone missing and the attacks seem to intensify daily.

- There are rumours that one of the crusading Astartes have fallen to madness and he is currently roaming the streets, gathering anyone nearby who will listen. There have been no attacks yet, but what is he doing with so many people?

Be sure to mix both social, combat, and good ol' problem solving in there.

Thanks for the ideas, they're all great. I already have a few characters developed for the faction that has the strongest claim on the world, and I'll probably take a fairly feudal approach to it. Followers of Khorne will be left over from the crusade, and I think there will also be Necrons awakening.

A political intrigues in a hive where chaos now rules? Oh wow.

First of all, a hive is a layer upon layer of social conflicts which are barely held by the force of Imperial Law.

So, from spires to underhive

Noble Houses (those smart enough not to declare loyalty to chaos to soon or too late as the chaos sieged the hive) have feuds running for millenia, but now nobody would mind them clashing in open wars and selling their very souls for power and vengeance.

In place of (or directly from ranks of) Ecclesiarchy new pontifexes rise - usually using piles of their followers as stairway to acsention.

Administratum is gone, few care about thrones, and while gold, pieces of art or supplies could be used as a currency it all mostly degrades to barther or ritually sealed contracts. Internal economy collapses whithin a week.

External economy is no more either. Noone sends ships to be filled with hive's industrial output - black crusade probably took every gun and every hiver they could store in the bellies of their ships and could not care less what happends to the hive after they take off for more glory. Noone sends ships with agricultural supplies either - horrible hunger consumes the hive immediately.

If you thought going is tough in the spires, you should visit hab-levels where the majority of hivers live. Arbites are no more, might makes right and you can be robbed, raped, tortured, killed, eaten alive and sacrificed to the Dark Gods (in any order) way faster than it was under Aquila. After the killings of most wise savants of the machine god new, young rulers of manufactoria embrace fusion of warp and tech barely knowing the basics and conduct experiments so inhuman that nazi camps pale in comparison. Street-level cults, like in the good old imperial days promise salvation from pain and fear, only now you have a good chance of being unlucky enough to get an answer from your object of worship. Absence of food, clean water, basic supplies is much more evident - corpses of people who died from starvation and disease rapidly outnumber those who died violently. Soon entire hab-levels are inhabited only by ghosts. All in all, if you ask the guy from an average hab-block, he would have rather died quickly during initial assault and mass slaughter after it or at least gone with the conquerors bound in chains - enslaved they would have better chances to survive - or so they think.

Underhive hardly even felt something has changed at first. But when it did - every single scum, mutant and ganger rushed upwards, hungry for fresh air, living space, blood of the upper's men and flesh of their women.

And those strange and scary things that inhabit every hive's ancient tunnel works, sealed blocks and forbidden levels, things that are used to scare the children, things that are present only in the scary folk stories never considered seriously - they slowly awaken.

That's quite the description. Thanks for the help, and I'll definitely keep that all in mind as I go forward.

Here is my offering to your setting (which I really want to give my thumbs up for the idea!)

https://www.dropbox.com/s/j1i81t43qow62s7/HouseOfJack.pdf

Since it would have made for a LARGE post, I turned into into a plain text PDF download instead.

By the by: What is your Player characters Goal in this?

- do they just try to life their life and Profit of the squabbling of others?

- or do they try to build up their own power base, gaining territory and followers as their infamity grows?

The Jaws
Some mutants fled into the underhive. Deep down there, far from men. Not much light there, even less food. Donw there, you survive or die. Those who die get eaten. You need to eat. You need to survive. If you are cunning, you eat steal from men. You steal there things and you steal them to eat there flesh. You eat the flesh of your own, too. You are vicious if you survive. You will bend up with other, but not with to many. There is not enough food if you are to many and once you turn onto another you will never trust another anymore.
Days go by without being days. Nightcycle and daycycle have no meaning no more. You rest when you are tired. You go hunting before the hunger becomes to much to bear. If you are cunning, you learn the times when it is easy to prey upon men. You avoid the armed men that are send down once in a while.

Then, it all changed. First there were dreams in your sleeps. Strong and feverish. About fighting. About going up in numbers larger then ever. About eating men openly on there streets. About a mighty roar from dozens of your thorats as one and your teeth red with blood and your gullets warm from the flesh of men.
The he came. You felt him before you saw him and he has felt you before he saw you. He head many with hem and he did not need to say nothing. You saw him and you knew and came to his side. You wanted to eat. You wanted to go about. You wanted blood on your teeth and flesh in your gullet, too.

“The Jaws” were one of the many disorganized mutant groups surging up from the underhive like upon a hidden command. While mutant raids where not unheared off, they never had happened in such large numbers before. And not all at once in different spots. The Jaw were lead by a wyred and in the first days they were simply rampaging through the hab stacks, killing and feasting on men . They teared men asunder with their teeth alone and those mutants who would not join them would be devoured, too. As the old order was gone and “the reign of the Mutant” had come, the Jaws became a horde of about 40 cannibalistic savages still lead by the wyrd that had brought them up. And the wyrd decided to change tactic.

When the Jaws reach an populated area, they will send a messenger. “Fyyyvvveeee men…..fully grown..no matter women or not…..give or we take all!!” The stories of the fate of those who did fight are nasty. The Jaws worship chaos as a whole and the gifts there members have are many. So some still bear weapons, most don´t have to anymore. And they all want to have blood on there teeth and flesh in their gullet. They always welcome new mutants into their ranks...unless their number is as large as about fourty. Then, the one that wants to join the Jaws will have to fight somebody that is already part of the Jaws, chosen by the Wyrd (usually: the weakest link of the Jaws). The winner eats the loser. If your teeth are red, you are one of the Jaws. And if your are one of the Jaws, your teeths grow...
In days like these, most have no qualms of giving a way five lives and so the Jaws see less fighting the at the start...and some of the mutants frown upon it, but nobody questiosn the wyrd by now. There was a story of a Khornite "hired" to defend a settlement who replied to the demands of the Jaws by challenging them to name a champion for fight to the death. Eight men if they would win, none I they would lose. The Khornite won… and howling in scorn, the Jaws moved on.

In your game the Jaws can be used something that roams about. Have the characters –hear- about it, about what they are and do. Then, have them learn that the Jaws are near. They can attack something the characters want to protect. They could simply show up to demand five men… which the characters might simply give them to avoid problems. The characters might coerce them to attack a rival or bargain such a thing with them (“10 men if you attack the nearby settlement instead!”). Our your PC might take out the wyrd leading them to see the group scatter. Or they might try to convert the whole horde to Khorne.

One word.

"Redemption!"