Traits add an extra layer of customization to Pathfinder PCs, one that I am particularly fond of because of the way they can support choices in background. Here are some Planescape regional traits as developed on the Planewalker Forums (original thread) that I use in my home campaigns.
Regional Traits List
Cager – Sigil
You have spent most of your life inside the City of Doors and its strange ways and urban lifestyle seem natural to you. You gain a +1 trait bonus on Knowledge (Planes) and Knowledge (Local: Sigil) checks, and one of these skills (your choice) is always a class skill for you.
Canter – Sigil, Gatetowns
Sigil is a city of many voices and more tongues. Growing up there your ears are accustomed to untangling the cacophony. You gain a +2 trait bonus on linguistics and linguistics is always a class skill for you. Furthermore, you are able to understand the local cant of Sigil without problem and get a further +2 trait bonus to linguistics to understand such things as scramble speak or dabus’ rebuses.
Expatriate – Prime
Planars always wonder why gods spend so much time worrying about the Prime when the Planes are so much more obviously important. You’re from the Prime, though, and you know that the masses on the Prime are where the action is. Some of that radiates when you’re dealing with the servants of deities. You get +1 to Diplomacy and Bluff checks made against celestials or fiends. [contributed by Jem]
Gray Soul – Gray Waste, Hopeless
You spent too long on the Waste and some forgotten part of your hopes and dreams died away. It’s hard to play on those themes with you. Any attempt to fascinate you, be it by spell or bardic music or other ability, has a -2 to the DC. [contributed by Jem]
Blood Contract – Gehenna, Gray Waste, Baator, Acheron, & associated gate towns.
You grew accustomed to the ways of devils and loths; perhaps you have a little arcanaloth blood in your veins. Once per day you may sign a contract with your own blood to put all willing signatories (except you) under the effects of a Lesser Geas with a caster level equal to your hit dice and terms as written in the contract. The affected creatures must willingly sign the contract and you need not be a party to the contract other than as a signing witness.
Undue Persecution – Acheron, Baator, Gehenna, & associated gate towns.
Growing up on the plane of tyrannical order has sharpened your wits to a knife’s edge. You gain a +1 trait bonus to Diplomacy and Profession (Lawyer) checks and one of these skills (your choice) is always a class skill for you. This bonus increases to +2 if being used to help someone (including yourself) get away with or frame someone for a crime.
Perfected Processing – Mechanus, Automata
Though many subcycles you have developed a fine knowledge of how to properly work within the letter and spirit of the Law. You gain a +1 trait bonus to Diplomacy and Profession (Lawyer) checks and one of these skills (your choice) is always a class skill for you. This bonus increases to +2 if being used to get through bureaucratic paperwork and customs.
Pattern Recognition – Mechanus, Automata
Some might think that having lived for so long on a plane where illusions are impossible would make you a sucker for them, but as it turns out some of the plane’s own resistance has rubbed off on you. You get a +1 trait bonus on saves to resist illusions, since something tends to seem off about the patterns they impose on the world. [contributed by Jem]
Plays Well With Others – Arcadia
Time on the plane of community has helped you learn to work smoothly with allies. When you are using the aid another action, your friend gains a +3 bonus rather than +2. [contributed by Jem]
Due Process – Mount Celestia
You have been raised to uphold the law for the greater good and know how to apply it in service of justice. You gain a +1 trait bonus to Diplomacy and Profession (Lawyer) checks and one of these skills (your choice) is always a class skill for you. This bonus increases to +2 if being used to defend an innocent or bring the guilty to justice.
Inured To Chaos – Xaos, Bedlam, Limbo, Ysgard, Pandemonium, Abyss , & associated gate towns.
You’ve lived a long time in a place where sudden random upheavals are part of the background noise. When you’re flat-footed, you gain a trait bonus equal to 1/2 dexterity bonus to AC.
Blood of Fire – Fire Elemental Plane, & Related Quasi-Elemental Planes
Born and bred with the ever raging inferno of the elemental plane of fire. You are able to cast Produce Flame 1/day with your HD as the caster level.
Body of Stone – Earth Elemental Plane, & Related Quasi-Elemental Planes
You descend from the great and infinite seams and layers of stone and earth with the power of Elemental Earth in your blood and bone. You gain a +1 trait bonus to DR.
Dive training — Water, Ooze, Sand, Salt, Dust, any primarily submarine planar layer
You are an air-breather who has practiced and trained in working underwater for long periods. With 2 rounds of preparation, you can hold hold your breath longer: 3 rounds per point of Constitution before beginning to make Constitution checks, which start at DC 5 rather than 10.
Benthic Adaptation — Prime and planar oceans (not Water or Ooze)
You are inured to the deep. You never suffer from environmental high pressures (usually deep water) and need not make Fortitude saves to avoid pressure damage. You never take nonlethal damage from, or get hypothermia from, cold water; this does not apply to atmospheric cold, or ice.
Lightvision — Radiance, Lightning, Fire, Positive
Your eyes are long since adapted to brilliant light displays. You are never dazzled. Against effects that may cause blinding from bright light (GM’s judgment, but obviously including spells such as glitterdust, sunbeam, color spray, radiant burst, etc., but not blindness or power word blind), save separately for that effect and add 1/2 your HD to your roll.