Here are some example campaign hooks for Dark Sun.
Here is a great resource from a now deleted Dark Sun Site, The Deadlands of Athas (doc) by Gerald Arthur Lewis.
There are strong rumours about a druid conspiracy or even a druid army in Athas. During the Great War, druids were hunted to near extinction. They had to form secret networks to join forces to better protect one another. Over time, after the war, those druids would have had the opportunity to grow in numbers again, maybe plotting revenge and/or seeking to restore Athas to its former glory.
This campaign can assume different styles, depending on what the motivation of the druid army is, what their style is (subtle? aggressive?) and at what stage in their goals the druids are.
A mysterious group of druids appears from time to time and inflicts great changes upon the land or sabotages a Sorcererking/-queen. They proclaim that their time has come to fight back. Mysteriously, no trace can be found of these druids. Are they under the protection of the Pyreen or other good forces? How powerful are druid spirits? Who leads them? The players could investigate for a Sorcererking/Defiler, try to join the army or both.
The druid army has many spies, many agents. Often, they don't know who they are working for. The druids fight with the methods of the Sorcerermonarchs. The goal is to bring the former Champions down, but when is the right moment? Is it now, the time where half of them have been erased already?
Genasi (see New Races section) are the offspring of an elemental creature and a humanoid. The ideas for this campaign is based on the power struggle between the elements and para-elements and the struggle between the elements and defilers, especially the Sorcerermonarchs.
The elements, longing for a stronger influence on Athas, could have persuaded some of their most commited clerics to produce half-elemental offspring. These offspring are functioning as agents for the elemental powers. It is however possible, that a genasi is not always doing things in their parents' will and sometimes, the non-elemental parent has other ideas about power than the elements...
Examples for a Genasi campaign:
Para-genasi (with the exception of rain-genasi) are engaged in a small-scale war against "true" genasi, using cleric and other people as their pawns.
Genasi are trying to find allies (e.g. the Veiled Alliance, druids) to assist them in their mission to restore Athas. This could even mean to work against the remaining Sorcerermonarchs.
The genasi try to build land of their own (almost like the Champions did before starting their metamorphosis) in a remote area from which they want to challenge the rest of Athas. They might be harsh masters with a ruling style not much different much from that of the Sorcerermonarchs - or they might indeed be very kind masters, depending on the respective genasi. The campaign could be either centred around one genasi as a ruler or around several genasi with different ruling styles struggling against one another.
Windriders of the Jagged Cliffs gives examples of pretty disturbing products of life-shaping activities.
At the moment, there has been a resurge of interest in what could be called 'bio-weapons'. Life-shapers who have been critical of this and who have crossed people's paths, have either been expelled or disappeared. This sounds like a good foundation for a campaign of 'evil' life-shapers versus expelled 'rogue' life-shapers.
The "bad" rogue life-shapers are influential figures in the official life-shaper guild. Some of them are 'truly evil', others have been made pawns by using mind-controlling/personality-altering symbionts. The person on the very top is unaware of what is going on. He is starting to become a bit disturbed about the increasing reports of life-shapers being expelled, but he is shielded from what is really going on. If he found out, he would he shocked, but also, his life would be in danger.
The evil life-shapers have so far managed to explain any discovery of their experiments on their enemies, the 'rogues', thus leaving these 'rogues' with no means to defend themselves and with no option but to try to escape and fight their enemies from the outside. But a few loyal friend remain inside...
A Bioweapon Campaign would be centred around (dark) ancient life-shaping secrets. The "baddies" want to abuse them for power, of course, and, to make things worse for the PCs, they are extremely influential and can manipulate people with artefacts, so that the PCs never know who they can trust.
In addition the evil life-shapers pose a threat to the Sorcererkings once they have powerful enough tools. A Queen/King could even send PCs to investigate matters when strange artefacts start turning up (by either contacting rhul-thaun or transforming non-rhul-thaun PCs temporarily into rhul-thaun?).
The "bad" life-shapers (you could call them Pur-yihn or Ban-yihn etc.) have put together several groups of mercenaries they are sending out to discover ancient artefacts. Often they are ordered to very specific places. The Pur-yihn know that these people might easily die, overlooking ancient traps or raising deadly life-shaped creatures.
None of the mercenaries knows the real people behind this organisation. They just know of a mysterious dark figure (who is only a middleman - but how can they know?)
The Pur-yihn have allies among the water clerics and the government. You could have the neutral priestess Hiv-anad killed and replace her with an evil priestess called Ghoun-apish (or change Hiv-anad's alignment). The water-clerics already act as spies, but now they give work more efficiently for people like like Gil-ogres, the Chief adjutant of Loi Far-oneth, the Master Lifeshaper.
Another thing the organisation could be responsible for is the hunt on fire clerics. What if fire clerics do not only have a negative destrucitve influence on life-shaped matierial? What if they are the only people who can oppose and destroy new biomechanical weapons or what if they can, for instance, construct life-shaped "flame-throwers" who can destroy other weapons?
On the other hand, there could be evil fire-clerics among the Pur-yihn, but this knowledge is, of course, hidden from the other life-shapers.
The "good" life-shapers in our campaign are led by Wem-osun (p.62 WotJC). They could also be led by other "rogue" life-shapers who have no support at all and who have to fight against all sorts of prejudices (before people believe them...).
This is our favourite solution for people who want to remain flexible:
The Mindlords (of the Last Sea) - or just one of them - finally managed to change the time-line. Athas looks different now and you can decide for yourself how different it will be - it does not have to be that different. There could be gods on Athas, a large body of water, surviving Rhulisti etc.
You could even use the "Worldbuilder's guide" for a random outcome. Alternatively, you could have your players realise that something is wrong and investigate the matter. If they find out and manage to change it back, it does not necessarily have to change back to its original state!
While the official line is to enter the 'Age of Dregoth', other campaigns around the former Champions are possible.
The campaign could be set before the official Athas timeline, e.g. during the Cleansing Wars or before the Deadlands came into being.
The PCs are members of the resistance or allies of the Champions.
Current events could also be altered.