Reddit reviews Pathfinder Roleplaying Game: Ultimate Campaign

I use two books:

• Magical Medieval Society
  
  
• Pathfinder: Ultimate Campaign
  
  The first is very detailed and dense. It's more about how the structure of society functions, which can lead to roleplay; the latter is more adventuring specific.
  
  The book on medieval society will seem, at first, to be needlessly pedantic, but the point isn't really to make the players know all that stuff. It's more just giving you lots of detail that you can then pull out the parts that might lead to something interesting. Let's say they own a manor. Who's land was it previously? They need people to work it. Did they steal those peasants from another lord who now hates them? Are there druids that live in their forest and are they angering them by their constant logging?
  
  

OK let's get really random here and generate a backstory using the background Generator section of the Pathfinder Ultimate Campaign book (pg. 16-51)! I will adapt a few things that aren't in it like tiefling family dynamics as well as not worrying about traits and their bonuses as we are talking about 5e.

First pass as to reduce the number of times to call the rollme bot will require more than one, after each pass I will parse the rolls into results and add into our list of backstory points.
Second pass we got some great results that work pretty well already, only a few more rolls for the final details.
All Rolls Done now we figure this all out...

The Tiefling was born into a young family in a large town. Peasants to begin with, they faced even more hardship after Razjio's other worldy features were seen by the townsfolk. What little work they once had dried up, and soon they were in the streets as beggars. A third child a year later meant that many nights the devil-boy went hungry. Seven winters after his birth both his father and mother succumbed to the sewer plague. At that point he made his way to (insert campaign specific city) never seeing his older brother or his younger sister since. After a few failed attempts at pickpocketing he found his way into a monastic orphanage.
After years of silent study and transcription the young Razjio was elevated to the Order of the Body, the martial sect of the brothers. He took to his study with a certain zeal but even though he trained just as hard as the other initiates his waistline continued to grow. What the brothers did not know was that he secreted away any food he could acquire and gluttonously ate it at times of stress. No stress was greater than his first experience with love. Griselle was a lovely girl, probably the first to actually show any romantic interest of the young lad. After a brief affair her father, a middle level Bishop of (insert LG god)'s temple, she was sent away to (insert far flung city that would require great wealth for our PC to go to) without Razjio's knowledge. After finally learning of his loss he made his way to the temple of Hades and swore an oath of revenge against the holy man. A cleric of the temple then approached him with a plan. Hades had passed to this cleric some deeply embarrassing information about Griselle's father. It seems that the old fart had been embezzling a lords amount of temple funds away for himself and a second family that he kept in (insert "suburb" of city). Razjio called upon brother (pick name for The Hunter), the monk who ensured his entrance into the Order of the Body, for help in bringing this information to the Archbishop of (LG god) with the most quickness. Within a fortnight her father was striped of his title, excommunicated, and thrown into the dungeons below the city.
The damage was done however as Griselle was gone, far out of Razjio's current reach. Even with her far away he only entertains thoughts of her in his heart.
He now is ordered out into the world to do the bidding of his Order but he tends to look for ways to benefit himself first with a special eye out for a new meal to taste.

Hopefully that might work...

Step 1 - Homeland, Family, and Childhood (Tiefling stuff adapted mostly from Humans)
-Race
Already rolled: Tiefling
-Homeland d100:2 - Town or Village
-Parents d100:95 - Both of your parents are dead.
-Siblings d100:62 - 1d2:2 - 2 Siblings - 1 is older and 1 is younger than you.
-Circumstance of Birth d100:21 - Lower class birth (roll 2d20 on parents' profession)
-Parents' Profession d100:86 - re-roll as per Lower class birth 2d20:23 - Serfs/Peasants
-Major Childhood Event d100:50 Troubled First Love: Your first love was everything you imagined it would be. That is, until you were separated from your beloved. This may have been the result of distance, changing perspectives, death, or differences in class or family. Some have said this made you jaded—you think it has granted you insight on how the world really works. You roll a d12 instead of a d20 on Table 1–56: Romantic Relationships. (result is a 11 already so we'll keep it)


Step 2 - Adolescence and Training
-Monk Backgrounds d100:2 - Belicose Historian: What started as a scholar’s curiosity in exotic fighting styles bloomed into a fanatical desire not just to learn about martial arts, but to master them.
-Influential Associates d100:1 - The Hunter: This person was a lone wolf who nonetheless cautiously allowed you to become a member of her solitary pack. She taught you how to thrive on your own in spite of the many perils and natural dangers of your native environment.


Step 3 - Moral Conflicts, Relationships, and Drawbacks
-Conflicts d20:5 - Humiliation: You publicly humiliated or scandalized someone with either true or slanderous information.
-Conflict Subject d20:8 - Clergy
-Conflict Motivation d10:4 - Religion
-Romantic Relationships d20:11 - Current Lover
-Relationship with fellow adventurer (included only as inspiration) d100:3 - Family or as close as family, d100:59 - Former fellow inmates or former inmate and captor, d100:84 - follow (or followed) the same faith or cult
-Character Drawback d100:37 - Pleasure: You crave luxury, entertainment, and pleasure. You might indulge in every passing fancy or hold strong against a temptation that constantly eats at you.


+/u/rollme

Pathfinder has a book called "Ultimate Campaign" that has a lot of rules for building anything from a castle to an entire town, from running a guild to a city, to an entire Kingdom.

The rules are close enough to 3.5 that you should easily be able to adapt them. It's rather interesting, they use things like construction points (iirc) etc that are generated by the amount of resources the area you control has (and which can be bought with gold). It could be a good baseline for what you need.

It even has rules for building and recruiting armies, and having large scale battles and wars. It's quite fascinating really.