Here is a brief overview. More follows in due course.
The name of the world is Salta; the principal language of the few civilised places on this world is Saltese and natives of the world are also known as Saltese. Hopefully, this will confuse the players into thinking that there is some connection between Salta and Malta. There isn't.
Neither is it particularly salty.
If you really must have a reason for the name, derive it from saltire (a diagonal cross, as opposed to a Maltese cross, which is horizontal and vertical). Flags and emblems on Salta often use saltires.
The world of Salta is anachronistic. There are two comparatively modern-seeming, civilised city states, Ja Wigenzaicia and Asaxonglial Casary (the names don't mean anything - I made them up). Outside the city states, there is only wilderness.
The two City-States, Ja Wigenzaicia and Asaxonglial Casary, are at war. They don't particularly want to be at war, but they have no other way of settling disputes. In past times, there was little contact between the two City-States, but in recent times people regularly travel between them, so disputes are becoming more and more common. Tradition dictates that disputes are settled by combat, so disputes between city-states are settled by warfare. So there.
Fortunately, the areas of influence of the two City-States are separated by a wilderness known as the Werelands. All of the fighting takes place there. Anyone peacefully-inclined just has to stay out of the Werelands.
Both City-States have grown wealthy by exporting the produce of the wildernesses to other worlds.
Modern Saltese like to believe that they have to travel offworld in order to learn true magic. This is not quite true: there are still a few true magicians in the various wildernesses whose magical talents result from the non-human part of their ancestry. All wealthy Saltese travel offworld extensively, both as part of their education and to learn magic. This was relatively unusual as little as a generation ago, but is now universal amongst the rich and starting to spread to the middle classes. The favoured destination varies from person to person, and might be (for example) Atlantis, Megalopolis or Vlydyga.
Native Saltese have no psionic powers (although offworld immigrants might). Most of the locals simply do not believe in psionics (this will probably change in the next few years, as more of the middle classes travel to other worlds).
Thieves as such are relatively rare on Salta. In a merchant society it is easier to steal other people's money by accountancy than by picking pockets. However, gymnastic competitions and acrobatic displays are popular. About one person in twelve has enough training in gymnastics or acrobatics to be considered a 1st-level thief.
Although anachronistic, old-fashioned warrior training (chain mail, shield and sword) is still relatively common. The generals (most of them high-level warriors) maintain that warfare should be practised in the old-fashioned way, with armoured knights hacking away at one another. Although Saltese civilisation would be perfectly capable of inventing firearms, bombs and poison gas, most civilians do not want to be shot, bombed or gassed, so agree with the generals.
About one person in 300 has enough warrior training to be considered a 1st-level fighter. Although many of these are in military employment, at least as many are professional or amateur athletes (some of the gymnastic competitions get rather rough). At higher levels, successful athletes outnumber generals and senior NCOs. A few truly old-fashioned high-level warriors move to the wilderness and build themselves anachronistic castles.
Priests and priestesses are commonplace but regarded as rather old-fashioned. They honour the old Saltese deities and scriptures, which maintain (in contravention of obvious fact) that Salta is the only world on which humans live. Both of the City-States are home to over a dozen high-level clerics, most of whom are undecided about the functions they should perform in the modern world.
Any adult native Saltese who wants them can cast low-level clerical spells, a gift from the Saltese deities (who are getting desperate as native Saltese travel offworld and encounter other religions). Some people are so fashionable as to decline them. The spells awarded will typically be one 1st-level spell plus any which the person would be entitled to by virtue of high wisdom/intuition. The spells awarded are decided by the deity in question. They will typically not be all that useful to adventurers. Unlike the spells awarded to natives of Wregin by their indigenous deities, the spells awarded by Saltese deities may not be all that useful to anyone else either (since the Saltese deities are not all that well-organised) and they cannot be used on any world other than Salta (since the Saltese deities do not believe that there are any other worlds).
The ruler of Ja Wigenzaicia is Hicaramehoette, who was born in Ja Wigenzaicia but educated at the Institute of Conjuration in Atlantis. Hicaramehoette's tutor at the Institute has since died, and she does not get on particularly well with its current head, Rallexia Lahape.
Oddly, although Hicaramehoette is a hereditary ruler, she has no formal title (she is not a Queen or a Princess or a Duchess or anything like that) and is not addressed in an overly deferential manner (Your Majesty or Your Highness or Your Grace or anything like that). She nevertheless has the important things associated with hereditary rule, including a palace and a loyal general who heads her army.
[AD&D-Specific] Hicaramehoette, human female, born on Salta. Str 13 Dex 10 Con 16 Int 13 Wis 15 Cha 11 Align NG Hp 50. Height 6'1", Weight 158 lb. Conjuror, level 15.
Hicaramehoette needs to make use of her magical skills to hold on to her position (there is a large faction in Saltese society which disapproves of offworld travel), so she continues to rise in level.
Hicaramehoette is a scholar with all the advantages and disadvantages of the scholar kit. She has the ability to read magic eight times per day. She has the keen eyesight and light sleeper traits. She has two specialist spells, mount and glitterdust, is immune to grease and other slippery spells, and (like most of the upper class) does not cast spells from the school of necromancy.
As a Saltese native, Hicaramehoette can cast three 1st-level clerical spells and one 2nd-level clerical spell when living on her home world. They are not spells useful to adventurers and have no game effect.
Hicaramehoette is of the school of thought which believes in carrying few, but powerful, magical items rather than many lesser ones. Her principal weapon is an adamantite dagger, +5, through which she can cast glitterdust at will (this is the one and only magical item she has created for herself). She also has a unique wand which enables her to cast conjure spell component at will and wildstrike once per day. The only other magical items she uses are a ring of djinni summoning, a robe of stars and an amulet of life protection.
Hicaramehoette has studied glitterdust deeply - it was the subject of her graduation thesis - and she can cast it in any metallic colour.
Hicaramehoette is a member of the Teleport Society.
Hicaramehoette's younger sister Priejkouxlia has already been described as part of the introductory scenario set in Vlydyga. Priejkouxlia studied enchantment at the Institute of Enchantment in Atlantis as a pupil of Bzaran the Genocide. Priejkouxlia knows and is on good terms with Xukry.
[AD&D-Specific] Priejkouxlia, human female, born on Salta. Str 7 Dex 10 Con 11 Int 15 Wis 9 Cha 17. Align CG. Hp 20. Enchantress, level 11.
As a Saltese native, Priejkouxlia can cast one 1st-level clerical spell when living on her home world. It is not a spell useful to adventurers and has no game effect.
Hicaramehoette's loyal general Villyjos has already been described as part of the introductory scenario set in Vlydyga.
[AD&D-Specific] Villyjos, human male, born on Salta. Str 15 Dex 17 Con 15 Int 8 Wis 14 Cha 11. Align NG. Hp 74. Ranger, level 12.
As a Saltese native, Villyjos can cast three 1st-level clerical spells when living on his home world. They are not spells useful to adventurers and have no game effect.
More details follow in due course.
An outline follows in due course.
The Werelands, although technically wilderness, is somewhat less wild than the other wildernesses of Salta. Most of the residents are either werewolves or weretigers. The werewolves keep out of the weretigers' way, and vice versa.
Both werewolves and weretigers are extremely annoyed about the influx, in the last couple of decades, of stupid fighters in metal armour. The stupid fighters charge in, hack away at one another for a while until there are a few casualties, and then declare that one side or the other has won.
It would be bad enough if the only result of this was that the Werelands was littered with dead fighters. However, it is not unknown for the fighters, while waiting for the enemy to show up, to take exception to the residents and start hacking away at werewolves or weretigers.
In recent years, the werewolves and weretigers have taken to getting their retaliation in first. And who can blame them?
These are good old-fashioned wildernesses, with good old-fashioned monsters.
Eventually, I may get around to writing some of these up. Until I do, you have a whole world to play with.
The Search for the Book of Macguffin is set in one such wilderness.
Player characters should be discouraged from using violence within the City-States (although if they want to take part in the rougher sort of gymnastic competition, that's fine). There are, after all, plenty of opportunities for violence in the Werelands and the other wildernesses.
The most common adventure in either City-State will be that the player characters are asked to join the army. It's voluntary, but the pay is good, as are the opportunities for advancing in level. All one has to do is accompany a unit to the Werelands, do a little bit of fighting, and return alive.
There are also adventures in the other wildernesses. For starters, there are those anachronistic warriors who are building good, old-fashioned castles. They themselves are busy supervising the construction work, so they are looking for adventurers to take on secondary tasks such as clearing the surrounding area of monsters. Again, the pay is good, as are the opportunities for advancing in level.
Then there are people who want to travel to the wilderness and will need guarding. There are merchants looking for new business opportunities (plenty of natural resources in the wildernesses), and sages looking to study indigenous Saltese magic before it disappears entirely. As this is genuine exploration work, with no nearby civilised base to return to, the pay is exceptionally good, as are the opportunities for advancing in level.