Beaten the game and looking for some challenges? Want to experience the really brutal side of Athas?
Here's some suggestions.

[All Challenges]
Difficulty: Hideous
Cheats: None
Ability Adjustments: None
HP Adjustments: Maximum at creation

Gladiator
No additional restrictions.

Scrapper
No half-giants, no thri-kreen.

Tribal
All party members of the same race.

Troop
All party members of the same single class.

Enchanted
All party members of only the following classes:
Cleric
Druid
Preserver
Psionicist

Disenchanted
All party members of only the following classes:
Fighter
Gladiator
Ranger
Thief

Elemental
All party members of a Priest class, either Cleric or Druid.
Each character must worship a different element.

Disarmed
No weapons, ranged or melee.

Enfeebled
Strength, Dexterity, and Constitution adjusted to minimum for every character.

Feebleminded
Intelligence, Wisdom, and Charisma adjusted to minimum for every character.

Frail
All characters adjusted to minimum HP on creation.

Enslaved (Shattered Lands only)
At least 3 party members are permanently AI-controlled.
You must play 4 characters.

Abandoned
One character only.

Parched
Resting and saving only in areas with a potable water source.

Poor
Cannot collect ceramics or sell items. Only quest and equipped items may be carried.

Mortal
Saving and loading only to stop and continue progress. Death is final.

Defiant (Shattered Lands only)
I spit in the face of Tectuktitlay himself!
Following the arena battle of 3 sligs and 1 mountain stalker, this dialog option with the announcer becomes available.
Choose it and defeat the monsters he releases.

Dune Runner
Complete as few quests as possible to reach the Final Battle.

Ssuran
Cannot use these items:
Dark Flame
El's Drinker
Living Cloak
Phrain's Bow
Shimmer Armor
Tanelyv's Armor
Terror Blade
Wind Ring

Templar
Cannot use these spells or powers:
Conjure (Lesser) Elemental
(Mass) Domination
Energy Containment
Entangle
Grease
Haste
Stinking Cloud
Wall of Fog
Web

Preserver
Kill as few intelligent beings as possible.
Arena and random encounters do not count.
Body count required! Post it here to the forums.

Rajaat's Champion [Choose a race]
All members of the chosen race must die.
No party members of the chosen race.
Body count required! Post it here to the forums.

Rajaat's Simulacrum
All other beings must die.
Body count required! Post it here to the forums.

Mix and match the above, see what you're capable of! I'll test and update these gradually.
Ideas are welcome.

I haven't played the game, but there are some other possible ideas:

No training:
You are not allowed to gain any levels at all. You must finish the game at the starting level.

Genocide:
You must kill every killable character in the game, except for the absolute minimum needed to complete the game.

Softlocker:
You must, as quickly as possible, put the game into an unwinnable state and then save the game.

Reverse Ssuran:
You are only allowed to use the items that the Ssuran challenge allows, plus any plot items which are mandatory.

Reverse Templar:
No spells, psionics, and powers except for the ones listed under the Templar challenge (once the list is made).

Edit: Here's another couple:

Magic-only:
You are not allowed to make physical attacks. Magic and psionics are allowed.

Poor stats:
You must adjust your stats to the minimum allowed.

And one for the sequel:
Low Level: Start a game of Shattered Lands, transfer your beginning party to the sequel (before doing everything else), and then proceed as per the "No training" challenge.

A fine brainstorm, but once you play the game you'll realize some of these aren't feasible for various reasons.

For example, reversing the item or power restrictions won't work because the restrictions themselves are so narrow. The point is to remove "cheese," or facilities open to the player that make the game way too easy. Most of those items you don't get until late in the game, and the powers by themselves probably won't have enough variety to win battles.

Level gain is also not optional.

I'm not sure I get the point of the soft lock. It's cute, but what's the point? Discovering the fastest stalemate? Genuinely neat, but I don't understand it. Most likely it would be killing a major character (like someone in Teaquetzl).

Genocide's a good one and strangely appropriate to Athas. It crossed my mind, but I didn't really consider it a "challenge." I'll add it anyway.

I don't think poor stats is doable at all... I say this because I believe the game enforces spell level restrictions, so you wouldn't get past the first level or so of spells for any mage/priest. Hit points will be terrible for your whole party, and on Hideous the damage disparity will be so glaring I can't imagine winning without reloading the game a shitload of times. I really want challenges that can be completed. If someone does then I'll add it.

Magic-only is essentially covered, but fists-only is a thing.

I guess we could change this to include Ravager challenges... don't think I can edit the title though. :/

If level gain is not optional, how about beating the game at the lowest level possible? Dual classing is not allowed. (Or, alternatively, with the fewest experience points gained possible.)

An alternative to poor stats is to only apply the rule to physical stats. This way you still get your spells, but you still have to deal with low HP, poor AC, and worse fighting ability.

Here are other ideas:

Low%:
Beat the game, but you aren't allowed to do any optional quests or explore optional areas.

Low% with skips (if possible):
As Low%, but if there are any exploits or glitches that let you skip mandatory parts of the game, you must use them. (Are there any such glitches?)

Single Class Challenge:
Choose one class. You are only allowed characters of that one class for the entire game. No multi-classing permitted. Optionally, additionally forbid psionics use (unless the class you chose was psionicist). If you choose Cleric or Druid, you may choose different spheres for each one. (Alternatively, require that every character makes the same sphere choices.)

Single Race Challenge:
Choose one race. Everyone must be of that race. (This shouldn't be too difficult, especially if you choose a race with few class restrictions.)

Pacifist:
Beat the game killing as few creatures as possible.

Ok, I mulled over some Dark-Sun-appropriate adaptations and updated the first post. See what you think. Thanks for all the input dtgreene!

As far as glitches, I don't believe there are any that help shorten storyline. I don't want to spoil these challenges for anyone, so we'll discuss exploits, like busted mechanics and cheesy or borderline strategies, in another thread.

I think the low level is covered enough by Dune Runner, since you'll be shortcutting a lot of stuff anyway. I mean you can build up xp in the arena initially, but it just doesn't feel distinct enough from the challenges already presented. That and there really aren't controls around xp. Farming isn't necessary at all, in either game.

Here's another idea I just thought of:

Rest preservation:
You may only rest if there is a tree or a body of water at least partially on the screen. Additionally, maybe extend this rule to saving as well.

I added saving since resting is already restricted in-game along similar lines. I'm not sure that either is really that challenging since Llod's Rod allows teleport, and I wouldn't really want to take that convenience away. But some critical areas you can't teleport so that's something.

Minor updates as well.

Here's another idea, after looking up the manuals online:

Poverty:
You are not allowed to carry or use any items except for plot or quest items. Temporary items created by spells (such as Flame Blade) are permitted. (It might be a good idea to avoid using thri-kreen, as they might subvert this challenge.)

Cure Prohibition:
The casting of Cure spells (and in Wake of the Ravager, Heal) is forbidden. The use of psionics or
non-cure spells to heal is permitted.

By the way, how much does Cell Adjustment heal anyway?

I always found Shattered Lands intensely hard, anyway. Playing with rolled stats instead of modified-to-max on normal difficulty was always plenty of challenge for me. Of course, I consider even that much madness on the true gold box games.

I agree. Shattered Lands is quite challenging without any self-imposed challenges for two major reasons; AD&D 2nd Edition Rules and the nature of the Dark Sun campaign setting.

Anyone who has ever played the pen-and-paper AD&D 2nd knows how utterly unforgiving the combat rules are. Even with the ability to make All-18 characters, this just adjusted your saves, AC and HP enough to increase, not guarantee, survivability. Second, Dark Sun is brutal, harsh and mercilessly Darwinian by design. In pen-and-paper Dark Sun, the PC attrition rate is so high that the player's guide in the boxed set flat out tells players to make three characters and to go ahead and start at level three just to have a chance.

The game is challenging enough, as you have said. There is no need to make the game impossible for "achievements". Beating either Dark Sun game is its own achievement.

As I remember Shattered Lands is not that bad at the beginning, but yeah tabletop it's absolutely brutal. Psionic everything is bound to be killer, since psionics has always been overpowered at the tabletop, especially in early levels.

The video game is a bit more forgiving, If you can beat or dodge the templars escaping the slave pits there isn't another really hard part until you've entered the the desert. More power to anybody who can handle Dark Sun with just about any of the handicaps discussed above, you're either a tactical genius or a patient reloader... you may well need to be both.

I know it feels this way, but trust me that once you've figured out how to handle the large combats, most of the battles up until the last one become more trivial.

As promised I'll discuss strategies and cheese in a new thread, but here's a simple cheese example:

Mass Domination by itself will allow you to beat the game with ease. They didn't implement it correctly so there's 0 maintenance cost, and you get up to 5x charm in one go. Train 2 psionicists in this ability, and charm all spellcasters plus up to 1/2 the remaining forces.

That's the cheesy way out, but there are plenty more reasonable options. You just need to figure out the magic side of the game, which is why I created a Gladiator challenge -- beat it on Gladiator (Hideous with no cheats or adjustments) and you'll see how much more fun the game can really be.

You said it yourself, it is an exploit. It is not that different from the spam exploit in Strahd's possession to eliminate the cooldown for the Holy Symbol of Ravenkind. However, exploits aside, i see no reason why folks can't challenge themselves however they wish. All I am saying is that as a vet of both AD&D2nd and Dark Sun, the game is faithful enough, bugs and exploits aside, that the game delivers Athas' harshnees quite well. If someone wants to challenge him or her self, feel free to do so. :) I did the same thing 22 years ago with Eye of Beholder.

Just my opinion, that is all. :)

Yep and as mentioned it is not required to beat hideous. Good strategy is enough. :)