I haven't written this up yet.
Should your players arrive here by accident, make things up as you go along, using the following as guidelines:
Havdazar is a city in the desert on the world of Delta. It is the capital of the Havdian Empire, which is large but, apart from the north, mostly desert.
The city of Havdazar is of lawful evil alignment. Its rulers, the Shahs, tend to go around invading neighbouring states. If short of inspiration, imagine how Nazi Germany would have behaved if (a) it had been in the desert, and (b) its hereditary leader had been a descendant of the One True God.
Only a descendant of the One True God can become Shah. This limits the number of candidates. Nevertheless, there always seem to be several qualified and ambitious people who want the job, and the life expectancy of a Shah is around a year or two.
The real ruler of Havdazar is the Vizier (yes, really, an evil Vizier - who would have thought it?). He has outlived several Shahs already, and in all probability will outlive several more. He cannot himself become Shah, as he is not descended from the One True God, and even if he could, he would not want to, as he understands abstract concepts such as life expectancy.
[AD&D-Specific] Umanyusnazeb, Vizier of Havdazar, Str 10 Dex 8 Con 14 Int 10 Wis 17 Cha 12 Align LE Hp 34. Abjurer, level 17.
In his youth (a long time ago), Umanyusnazeb studied abjuration in Atlantis. He hated the place. He also hates everywhere else that is not Havdazar.
The Shah has a large and well-stocked harem, one of the perks of the job. Several of the inmates have not actually slept with this Shah or any other - long before it gets to be their turn, the Shah exceeds his life expectancy and is replaced.
In terms of physical geography, the Havdian Empire vaguely resembles Kazakhstan.
The city itself would be a good place for the paranoid to go adventuring. If they do, make things up as you go along, using the following as guidelines:
Havdazar is a large oasis on the world of Delta. If you have an image of lakes and palm trees, forget it. It will probably be what the player characters are expecting (unless they have already been to Agvhazar), but it will not be what they get.
The desert sun is far too hot for standing water to remain in the open air. The source of Havdazar's water is an underground lake. Above the lake, there are several huge rocks, each the size of a small mountain. It is these rocks which keeps the lake relatively cool and stops the water evaporating.
The city of Havdazar is built into the rocks.
Social status in Havdazar depends on how high up you live. The Shah's palace is at the top of the largest rock.
Havdazar's main export is violence. The city maintains a large standing army. Ostensibly, the purpose of this army is to protect the tribesmen of the surrounding Havdian Empire from monsters. There are easily enough monsters in and around the Empire for this to be plausible.
Umanyusnazeb, the Evil Vizier, knows that armies standing around doing nothing get bored and cause trouble. For this reason, whenever there are not enough monsters to keep the army busy, he sends the army off to invade somewhere.
Normally, Umanyusnazeb sends the army off to invade a tribal territory somewhere. The usual result of this is that the tribal chief swears an oath of loyalty to the Shah, and the army proclaims itself victorious and returns to Havdazar. Sometimes there is fighting involved, but usually just the threat of violence is enough to convince the tribal chief of the merits of loyalty.
Sometimes, Umanyusnazeb sends the army off to invade a neighbouring Empire. He does not do this all that often. The problem is that a "successful" campaign might result in a neighbouring Empire ceding an area of desert to Havdazar. He is wise enough to know that increasing the size of the Empire by adding empty desert land is a bad idea. The army would have to be expanded in order to protect this extra territory, but there would be no corresponding increase in the resources of the Empire to pay for this.
Occasionally, Umanyusnazeb sends the army off to annex a small independent state such as Agvhazar. This is rewarding if it works. The main problem is that in certain circumstances it could be counterproductive. The small independent state might ask one of Havdazar's neighbours to defend it. If that happens, the small state will cease to be independent and become a satellite of one of Havdazar's enemies. Er, peace-loving neighbours. Not at all the desired result.
Umanyusnazeb maintains an extensive spy network, in order that he can reliably predict the likely outcomes of his various options. Even so, it can all go horribly wrong sometimes.
Havdazar has almost all the things one would expect from a desert campaign. There are snake-charmers in the city market. There are flying carpets. There are even magic lamps which summon efreet who grant wishes.
What is different is the atmosphere. Havdazar is lawful evil and oppressive. There is an enormous standing army looking for someone - anyone - to fight. Step out of line and there are tens of thousands of warriors out to get you. There are extensive spy networks spying on everyone, especially one another. Say the wrong thing, or the right thing to the wrong person, and everyone is out to get you. Even the efreet are paranoid. If you find a magic lamp and an efreet grants you three wishes, it will probably be looking nervously around to see who is spying on it as it does so.