The intention is for the players to save the citizens they know, the comrades-in-arms they risked death for, and the city they love. If they do one encounter per day, you should just narrate the consequences of that--gruesome murders and suicides, kids orphaned, cries for the city guard and the SRs to save them, diminishing faith in independence, etc.
I'll be running this soon. I'm going to have each PC narrate what their settled life would be like--kids, hobbies, business, crime-fighting, whatever. Then the Haunting of Kintargo and their old enemy calls them out for one last adventure.
I just started running this.
My PCs were just coming off their heavy handed win over the Chelaxian negotiators and happened to be in their manor on the northern border of Jarvis End and the Temple district. They heard muttering from the next room and entered the parlor only to see a pale old woman knitting on their couch. She was muttering to herself about the meddling Silver Ravens bringing doom upon the city. Eventually they heard enough and tried to wake her from her focused and despondent rambling. When they did her true nature became apparent; her skin immediately rotted and her eyes turned black. She floated above the couch and assailed the PCs with shrieks of agony. The Silver Ravens sent her back to death and her essence dissipated in wisps of incorporeality. Then, through the window behind where she sat in the parlor, the Silver Ravens saw dark churning clouds form above the Temple once dedicated to Asmodeus. I ended that session with the sound of hounds baying in a mournful chorus.
Mechanically speaking, I rolled my first random encounter of the haunting and it was a Banshee.
My best advice would be for you to ramp up your Random Encounters. Roll them long before your next session and create themes for them. You don't need to be bound by them. They're for inspiration only. Not every Random Encounter needs to be combat either.
•Have the PCs witness dottari fending off Shadow Mastiffs
•Have the PCs witness imps ripping slate tiles off of a roof in the markets of Redroof.
•Have a Hound of Old Kintargo ignite, snarl, chuff, and bay from a darkened alley only to disappear by way of dimension door. Then, have the PCs hear screaming from a crowd nearby. When they investigate (expecting the hound) they find two bone devils and a barbed devil binding a group of commoners in chains.
I have to preface this next part with reiterating that the corporeal outsiders the PCs face in this part seem to be summoned rather than bound. (The bodies return to their plane upon death)
That said, here's how I plan to handle each district: there will be a reprieve every time they beat a 'focus encounter.' After one is resolved, 2 to 4 days will go by where there is only rumors of hauntings occurring. Then, the hauntings are renewed and one of the districts will increase in power as written. This increases the tension and decreases the time it takes these encounters to escalate. In my opinion it also gives the city the feeling of being alive and allows the PCs a bit of time to collect themselves before another wave.
You are nearing the climax of a story that has taken your PCs out of the shadows and into the light. They were a rag tag group of dissenters and have become the saviors of the city. Don't skimp on the epic-ness that is going on in Kintargo. Discovering and untethering the focus encounters shouldn't take five days. If it does, you're really letting your PCs down.
No, actually I will be dropping things all at once, however given the nature of the pace they will most likely be unaware of the gravity of the situation. That means they will most likely be tackling whatever is in front of them at first and then as report come in they will start to see the bigger picture.
I have game in about 30 so I will have to give a more in depth response another time.