Note: I'm a long time casual Warhammer player in all formats (RPG, Fantasy Battles, 40k, etc). So while I know some about the fluff and history, I certainly don't know it all, so any discrepencies you will need to overlook.
My group got together last night for the first time in a few weeks. Last time we left them they had entered an Interlude. 4 months have passed, with Gilbert (the student turned apprentice wizard) having headed to Altdorf to further his studies, Lorenzo (the spanish sounding High Elf gambler) having bounced from gambling hall to gambling hall eventually finding himself in Altdorf as well, and Zil (the wood elf waywatcher) having been sent on the trail of the skaven witnessed in a previous adventure to Altdorf to investigate the possible skaven further.
But everyone in Altdorf insists Skaven are myths, so Zil is not having a lot of luck. The three companions bump into each other at some point, and retire to one of Gilbert's favorite watering holes. There a page from the Order of Celestial Wizards (Gilbert's order) finds them and tells Gilbert that he and his friends are wanted in the office of one of the higher ranking wizards. They go and are ordered to attend to a matter the city watch needs help with.
A short while later learn from the city watch that someone has committed a pair of grisly murders, and when a green glowing substance was found mixed in with the carnage the wizard colleges where brought in to help investigate. Back story note: The characters recovered a vial of the green glowing stuff and handed it off to the college in an earlier adventure, it turned out to be liquid infused with warpstone.
An investigation is launched and the party soon finds that the blood spatters are likely to have been caused by a firearm at very short range, and that the splatter pattern was actually manipulated to form an arrow at each murder scene. The arrows point away from a central point, but the maps of Altdorf are so bad that they can not accurately say where the intersection point is, but at least they have an area to look in. Two actually, as they think a third arrow may be soon found. They race to where they think the third arrow might be, but on the way are sidetracked by a blind woman in an alley.
She is dressed in tattered vestments of a priestess of Shallya, and has a bloody bandage over her eyes. The party is suspicious/concerned and in talking with her she relays a portent of things to come:
Three arrows, three rings,
Four deaths, many more deaths to come,
The fourth death is not just another death,
But rather the ultimate sacrifice to their bloated lord.
The party notices city watch rushing passed the alley and as they check it out, the crone disappears. They find the third murder victim has been found. With the portent in hand and the third 'arrow' confirmed Gilbert checks his notes and memory for any indication of what the symbolism might be and discovers that one of the symbols of Nurgle is three arrows and three rings.
They go to where they think the three rings would be and find a well at each location. They get guards to watch over each well and go to where they think the arrow tails should all meet. There they find an old boarded up house, that nearly oozes dread. Its hard for them to proceed, but eventually they do make it to the house (Discipline checks etc needed to force their feet to move).
Inside they find filth that only a cult of Nurgle could live in. They even encounter a nurgling in the filth, and quickly move on to try and not stay too long in the nastiness. They find a trapdoor that leads below and beneath the house the find a deep stair carved into the earth by hand. It ends in a small temple to Nurgle, complete with banners, cultists, a cult leader wielding sacrificial knife and strange pistol, and a sacrificial victim on the altar.
Gilbert yells that he must be stopped while launching a magic dart, and Zil launches a couple of arrows (rapid shot), while Lorenzo prepares to receive the horde of cultists. As the first arrow slams into the cult leader, he smiles. As the second arrow hits and kills him, he dies serving Nurgle, making the 'ultimate sacrifice to his bloated lord'. The sacrifice was a ruse!
The cult leader slumps dead over the altar, the ritual complete. All of the cultists scream as their lives are ended in the service of their lord, and the body of the cult leader begins to twist and writhe as he is consumed, his flesh and he flesh of his victim and cult members consumed to bring about the raising of a Plaguebearer!
The party is stunned momentarily but quickly recovers as it leaps atop the altar. Zil pins it there (with an immobilizing shot), Gilbert channels power, tossing another magic dart. It roars out a challenge, the room seeming to shift and change dimensions (can't remember the name of the power in the tome of adventure, basically gives the demon extra defense). Zil continues his stream of arrows, and eventually Lorenzo moves in to engage, blocking Zil from making his shots the next turn (actually Zil is cautious and rolled an hour glass while performing Rapid Shot. I dropped two recharge tokens on his Ranged Shot making him effectively not able to shoot for a round). Gilbert forsaw success for the party (First Portent, allows him to store a couple of dice for later use by the party).
Lorenzo managed to insult the cleanliness of the demon and his tidy followers (insulting blow) which only further enraged the demon who attack with a vicious assault against the gambler (go for the throat). Lorenzo is well used to drawing the anger of his opponents though, and between his thick leather armor, his parrying dagger, his high skill at parrying (parry with weapon skill) he was able to deflect each of the demons vicious attacks. He stuck the demon (die from portent used) again then quickly withdrew.
The demon responded by bringing out the pistol the cult leader had, it belched forth a nasty brew of warpstone and steam, slamming into Lorenzo. While his armor took some of the sting off, he knew that he would be feeling that one for days (6 points of damage made it through his toughness and armor, he only has 12 wounds total).
Finally having a clear line of site, Zil buried two more arrows (rapid shot again, with die from portent) into the demon, finally banishing it back to whatever pool of filth it crawled from.
Lorenzo's earlier thrown torch had caught one of the vile tapestries aflame, and the flames had spread to the beams supporting the roof, so the party beat a hasty retreat. Zil reached for the sacrificial dagger, but Gilbert stopped him, telling him it was better that evil be buried. Meanwhile Lorenzo slipped the strange pistol into his belt, pulling his jacket over it (skullduggery to get it passed the guards later).
The day was saved, the demon banished, but what is the pistol, and where did the cult leader get it...? Perhaps they will find out next time.