My goal is with these tables is to help make that tribe or orcs or bugbears you just rolled more interesting then just being "evil" or "chaotic". That said, a other solution can be to simply avoid using humanoids monsters and to use human factions instead.
Other interesting readings:
These tables assume that these monsters were simply "neutral" in the past and that something happened to constantly put them in harsh situations that lead to them becoming harsh and being considered evil by humans.
You can roll multiple times on each tables if you want to generate a harsher and more complex history.
The mystical past (d10) (These events happened a very long time ago, maybe 1d6 x 1000 years ago. Their stories focus on how their heroes have free their people from these hardships. There is also the possibility that the supernatural elements of these legends are interpretation of more mundane historical events)
- Their greatest guide or champion was corrupted by a powerful magical item.
- Their leaders were under the control of a supernatural influence (mind parasites, demons, etc).
- A evil deity or demon took over their old religion and corrupted their priests.
- A giant monster (dragon, giant, kraken, etc) ruled over them for many generations.
- A dark lord befriended or subjugated them for his or her own dark goals.
- A petty and vengeful deity cursed them for the "sin" of a important hero.
- A greedy or misguided leader made a dark pact with a dark deity and regretted it.
- They pursued a dangerous art or science that unleashed a disaster or a curse.
- They exploited a corrupted resource that slowly corrupted their bodies and their civilization.
- They were hunted or enslaved by a magic using civilization (elves, dwarfs, titans, immortals, etc)
The distant past (d10) (These events happened at least a 1d6 x 100 years ago) (different factions may have different interpretations of these events)
- They were exiled and forced to settle in a harsh or hostile environment.
- They were allied with a human faction that lost a major war.
- Their land was colonized by a human faction that was considered a enemy.
- The great war happened over their territory and devastated their lands.
- A positive leader or champion was assassinated and this created a moral vacuum.
- A corrupt dynasty supported by a outside faction ruled over them for generation.
- A natural disaster or calamity destroyed the new city they were building.
- Scarcity of a key resource destroyed their new way of living and pushed them toward harsher work.
- A booming and ruthless economy followed by a crash destroyed or ruined the new society they were building.
- A long and disastrous civil war violently teared them apart. The original conflict may be about allying themselves or not with a human faction.
What recently happened to stir the anger? (d20) (The first event happened 1d6 years ago, the second one 1d6 months ago and the third one 1d6 days ago)
- Trespassing: a human faction is establishing a route through their territory.
- Murder or hateful crime: a murder was committed on the tribe territory and accusations go both ways. (it could be a accident).
- Border dispute & skirmishes: local factions fight over the their territory.
- Land appropriation: a human faction claim ownership over their land and want to sell or exploit it.
- Population movement: the arrival of human refugees or settlers into their territory.
- Criminals: local criminals are hiding in the tribe territory. Humans accuse them of protecting them.
- Mercenaries: a mercenary band arrived in their territory to recruit new blood. Humans (and some of their own kind) fear their militarization.
- Rise of a biter leader: a biter and vengeful leader is rising in their ranks (or in a human faction targeting them).
- Scapegoating: someone have been wrongly accused of a crime or blamed for a accident.
- Rise of a populist leader: a populist leader target the other side and blame everything on them to gain political momentum.
- Corruption: a criminal or outside faction influence one of their clan or leader.
- Calamity: a natural disaster or plague devastate the land, blames go on both sides.
- Scarcity: a local resource is becoming rarer and force them to venture outside of their territory or human to venture into their territory.
- Succession war: a important clan leader died and the power vacuum risk to trigger a succession war.
- Bad trade: a trade with a human faction went very badly or was very exploitative.
- New predator: the arrival of a new monster push some of them toward human territories.
- Harsh competition: the tribe and the human compete over a trade or the use of a resource or a location.
- Attacks: orcs or human travelers were attacked by unknown assaillants.
- Rumors: new rumors about the tribe or the humans circulate and generate fear.
- Break of treaty or pact: a pact or a treaty was not respected or broken (by necessity, accident or malice).
How they are not always seen as evil? (d20) (You can roll multiple times)
- They respect the quality of one of the six attributes (STR, DEX, CON, INT, WIS, CHA) (You may use this stat for reaction adjustments).
- They master a craft and respect who master or respect it.
- They respect a common historical figure meaningful to a faction allied with the PCs.
- They respect the teachings of a old and still respected philosophy, religion, school, guild, army or faction.
- Some tribe members are know to work for humans (or to hire humans) and are appreciated for their competence.
- They like to trade goods and enjoy a good trade.
- The tribe have a mutual relationship with a faction allied with the humans.
- They always help strangers in a bad situation.
- Outcasts from their tribe live with humans and adopted human culture.
- They oppose a common enemy (for a relatable reason).
- They create and trade a unique resource.
- They have a good mentor of one of the PC class and respect members of the same class.
- They always show great hospitality and like to share food, drinks and laughters.
- They have beast companions that they respect and they show the same respect for other beast companions.
- They are very curious about the world and like to trade knowledge.
- They respect a old historical location set on their territory and respect history and who also respect it.
- They take great care of their sick and wounded.
- They show respect for their dead and to the land.
- They always honor a special greeting or sign that reference a historical alliance.
- They do everything as a family unit, children or elders are always present.
How dealing with them can be complicated? (d20) (again you can roll multiple times)
- Their language is complex and hard to master and require skill rolls to avoid errors.
- They eat something strange and hard to digest (but delicious).
- They dislike a type of gear and look down on it use, they may use a alternate solution.
- Some members of their society have specific greeting or introduction habits that can be complicated to honor.
- They dislike a type of teachings or religion from the PC's culture.
- They dislike a historical figure or hero from the PC's culture.
- They dislike a type of creature allied or beneficial for the PC's.
- They dislike a type of spells or magic.
- They dislike a allied faction.
- They respect a enemy faction for their own reasons.
- They have beast companions that seem repulsive or dangerous.
- They have a special character class that do something that seem repulsive. Like fire bugs eaters who vomit fire. They can eventually offer to teach that class.
- They have a dangerous combat tradition that buy social currency.
- They dont eat or drink a type of food.
- They frown on the use of certain material for a specific function. Like gold can be good for sacred jewelry but they frown on it use for coins.
- They have a different version of a specific historical event.
- They don't trust a character class and it methods (but they could be actually good at it)
- They ritualise a specific activity and it take a longer time to do it.
- They do a specific activity only at a specific time, location or with a specific person.
- They respect and refuse to kill a specific monster (or type of monsters) that the PCs have to deal with.