Hey there folks. I'm working on a new campaign focus for my Dark Heresy group, and was looking for a little input. Basically, my group to this point has been more Ordo Xenos focused, with some exposure to Hereticus and Malleus. My players have recently expressed a distinct interest in turning the plot all the way over to Malleus; they want to smite Daemons and wage war against Chaos. I'm shelving my Genestealer Cult for something a bit less subtle...

Current gist of my campaign is such; the party is recently returned to Juno after their stint on the frontier hunting down an Arch-Heretek. They've received kudos and praise for killing the guy, as well as rewards from the Tech-Priesthood for recovering an intact Warlord-class Titan from the clutches of the Green Menace. They'll have a week or two to settle in, get their new troops acclimated, reconnect with their contacts and friends. Then, a garbled Astropathic message comes through. It is intense, shocking, occluded. The Astropath will die a somewhat gruesome death in front of the party. Their last words will basically say they're feeling an echo of what is to come. Put them on high alert, mobilize things, have them searching for threats. Give it a few more weeks in game, let them settle a bit. Maybe put down a few hints about recent psyker culls going wrong, but overlay other, seemingly more important problems for them to investigate. If they go for the psyker thing, give them a couple poor leads/evidence it isn't a problem.

When they bite the wrong hook, I'm going to have the Bleak Pits erupt in a massive storm of Warp energy. Pandemonium (pun, not the actual storm) will envelop the planet as Astropaths start dropping like flies, Warp Incursions begin erupting at soon-to-be obviously set-up sites across the planet. The storm will stain the sky, mutants will arise in force, Daemons will marshal forth from the Warp to... Wage war on each other? It'll be a five-sided brawl as Daemons and their mortal or near-mortal allies clash with Imperium and other Daemonic forces across the planet. Some regiments will turn Traitor and dedicate themselves to blood, sects of nobles will strip away their veneer of piety and normalcy to embrace their desires, even a branch of the Tech-Priesthood will throw off the dogma and seek to change and evolve. As famine and pestilence set in, others will find Grandfather in their hearts, spreading like a plague from district to district. Psykers will start becoming even more common, psychic manifestations drawing even more Daemons and attention.

The party will first have to deal with local threats as their aircraft is grounded due to the storm. Putting down the local mutants rising up, assisting their contacts/friends/allies. Maybe finding a Daemon who is stiffening the rabble's resolve or finding a botched ritual site near their base. Stomping on a Possessed psyker or two as well. Nothing overly huge to start.

As their range extends, so will their perspective of how badly things are going. One of the bright notes will be that apparently the feral Orks of the swamps are joining the fray primarily against the Chaos, which helps out. The Grand Army of the Sovereign is being whipped in some locations, holding their own in others. The Vigil is having a difficult time controlling the populace, calling in Arbites support. The Dark Mechanicus infiltrators will have set off their more subtle sabotages, revealing their presence as the cause of the attacks against production in the area. Rumors of Chaos Space Marines should start spreading, as well as possible sightings of Daemonhosts. The local Witch Hunter whose attention the party has been avoiding should be prominent as a hero and warrior who is stemming the tide on the other side of the super-city. Rumors of Space Marines arriving any day should begin around now as well, and giving the party a chance to finally call an orbital strike against some kind of target (one of the Warp portals, probably) would be a good idea before it goes out of service.

From here I'm getting a bit foggy in my vision. Any tips/comments/concerns? Keep in mind, the game is at 14k experience now. They ain't newbs.

A great endeavour that is.

I always asked myself how I would do that, becaue it seems to me to be so big that unless you've got in your head pretty clear target to "stop" that sh*t from destroying everything, acolytes seems to me more witnesses than acting characters of the story. They are caught in a storm and must weather it, until it ends or they die with it.

But I don't think that's satisfactory in my own opinion, so I'm still thinking about how to do this, so I will be following the topic to see if there are good ideas, and post mines if they come!

I tend to make my campaigns have a handful of paths they can take, with consequences following whatever they chose; decide to investigate the Khorne cult? The heretek smuggler had time to develop and start shipping a new weapon-heresy. If they'd defeated the Heretek first, the cult might have had a full batch of Bloodletters instead of the one or two they barely managed to summon as you kicked in the door (thanks for the 64 blood sacrifices!). So, I'll give them opportunities to help various factions, target various foes in meaningful ways, etc. Each choice can hamstring a threat, while giving others a chance to fester and become more fun.

Interesting, so your players will be more taken at the beginning of said daemon war, rather in the full blown part of it.

I clearly misread your first post!

Since the warp is close to tear, you could have a lot of smaller cults also, that could be "false leads". I mean by this that players can get there and purge real cults, be these aren't the real architects of the coming destruction, nor will they have a strong impact on anything.

I would urge caution; depending on the players, a Daemon War planetside could easily lead to an Exterminatus...though in all fairness, that is one of the major reasons Exterminatus exists.

The trick is to make it appear worthwhile &/or winnable enough that the PCs don't just nuke it from orbit. Making it their home base certainly helps in that regard! Can't think of anything else from a gameplay perspective right now.

Narratively though, I got to ask; Why is Chaos Divided coming out in force here? The most reasonable theory is that they are fighting over some sort of resource. Which of course gives the PCs another objective/option; take the whatever the 'demons are after' away and maybe the Warp Invasion might stop.

Grim Darkness is nothing without a glimmer of hope occasionally.

Yeah, it being the Sector Capital and their base will probably keep the players from nuking it from orbit to be sure (though I don't have any doubts that there will be some precision orbital strikes). Inquisitors in the area likely won't because destroying the capital would have far too many negative ramifications.

My plan as to why is partially inspired by a few of the things I saw in Enemies Without. The Daemons got here due to clueless cultist activity timed with a surge in the Pandemonium (the cultists just followed orders, to their detriment) and the overall horrible condition of the Bleak Pits basically tearing real-space a new one in the area. Regions of the planet will be inhospitable/need to be scourged and quarantined after this, forever scarred by the events that take place. There will be resources to fight over, plagues to spread, blood to spill, changes to be made and I don't know, some kind of depraved orgy? Each contingent does have their own personal goals brewing in the back of my head, and preventing those objectives will help out a lot.

So, in the interim between campaigns, I've been working on ideas for this Daemon invasion idea, and one of them I'm really liking; a cult is making bound Daemonhosts at the behest of their malefactors, using limited numbers of bindings in concealable locations. These Daemonhosts are generally 'willing' to conceal their nature for a time, with the end goal being the infiltration of refugee camps and getting past the front lines to release havoc elsewhere. The first time the Acolytes realize what's really been causing all of this ruckus will be when they're targeted by what most would consider a plain, dumpy housewife refugee... Who pulls a Tainted blade and goes after the party before going down in a massive hail of gunfire, their condition only revealed after the inordinate amount of firepower it took to take her/it down. This will drag the Acolytes into taking care of this threat before it continues and starts breaking up Mankind from inside.

It keeps them involved, active and important while not having them on the front lines, waging war with the Guard.

A part of why I'm making this such a big event is because my PCs have sort of had too many unequivocal wins; I let a friend take over the game for a bit, and he ended up giving the party the opportunity to defeat an entire Ork army, which they did. It was over-much, and I'm sort of regretting giving him the opportunity without realizing how it'd go. They're flying high, sure of their victory. Since they asked for more Daemonic stuff (and have a stellar habit of blowing individual targets out of the water with massed firepower), I really think large numbers of Daemons are the answer (since they don't want to do Xenos stuff, which would have been Genestealer shenanigans full of intrigue and stealth); I took them through Dark Pursuits/Desolation of the Dead/Forgotten Gods before going to my own campaign; they defeated Suvfaeras as a Daemonhost, the Herald of Nurgle and Suvfaeras as his Daemon Prince self laughably easily; none of those actually managed to hit the party. Individuals will almost never threaten this party, as they have the power/capabilities to blow a lot of threats out of the water through sheer quantity of fire unless I just never have them encounter a fight with their war-gear. It takes units working together or just enough big threats they can't all focus fire on to make things interesting.

I want to actually stress the dangers/problems of Malleus; it's a war you can't really 'win.' While it may not look like it, you ARE outnumbered, you are basically trying to hold back the tide. My players don't really realize that; while I've explained it, I'm the one who introduced them all to the 40K setting and they haven't read much. It's an abstract concept to them and their characters.