The temple is a gigantic tower about 100 feet tall, at its top the elemental that it was built for lies asleep. On Athas there are no gods and the closest thing that comes close is the worship of powerful entities, such as elementals and some Sorcerer Kings.
The Prayer Room
Entering through the large stone doors you find yourselves standing on a solid stone floor, before you lays a large pit with small stone pillars enough for one person to stand. At the opposite end there is an altar sitting on an outcropping from the wall. Another stone doorway behind it. Three men in robes stand by the altar, swords at the ready.
Fluff:The room was created for common prayer, so often I'd see temples filled with needless deathtraps and other hazards not normally in a temple. The room is meant to have one person on each stone pillar to pray as such the fall from a pillar is only 10 feet so enough to do damage, but not to kill someone outright. The priests or priestesses would convey ceremonies at the altar, no the temple is in disuse.
Creatures can jump from platform to platform relatively easily though I required athletics checks to jump across. The enemies in the dungeon were simply reskinned soldiers and gave them the ability to hover. This works out better in 5th Edition because movement can be broken down to include an action while performing the movement. So an enemy could hover from one space, attack a player, and then return to an unoccupied space. Players could do the same thing if they had access to a flight spell. Aside from that I added abilities that allowed pushes, so if a player was pushed off the edge of a stone pillar they would have to make a dex save to stop from falling.
In the room, the floor is covered in sharpened bamboo pikes, four ropes lead from the floor to a hole in the ceiling 100ft up.
The room is a simple chamber to weed out the unholy from visiting the Elemental. The Priests would climb up to the roof of the tower this way. Air elementals that inhabited the tower would buffet those who were not of the temple, causing them to fall to their deaths.
This was originally a skill challenge where the players would have to hold on every 30ft of movement or be buffeted by errant air elementals that had taken up resident. So making athletics checks or acrobatics checks to jump from rope to rope while trying to climb up. My players were smart and decided to break the bamboo at the base of the tower to lessen the damage if they happened to fall. This was to their detriment later on however.
Before you lies a nimbus laying above the towerer, There is a large altar at the edge of the tower, but no railings for support. The Templar is chanting an evil spell as the nimbus begins to grow darker and darker.
This area was meant to allow the priests and priestesses to communicate with the elemental. As such they believed their faith protected them from falling off the sides or through the center hole in the level. This also allowed for them to perform executions of the unworthy if it was necessary. Typically they would challenge a fallen priest to climb to the top of the tower, if they survived they would be allowed to plead their case to the elemental directly, if the elemental felt they were lying or unworthy it would buffet them off the tower.
In my player's final encounter they actually managed to push a Mul Gladiator down the central hole. He survived unknown to them, if they left the bamboo pikes he would definitely have died.
This was a major boss encounter, the players had to deal with Templars trying to bind the elemental to their will and several soldiers that were to keep the templars safe while binding the elemental. If the Templar is harmed I performed a concentration saving throw to make sure the spell was not disrupted. After five turns the spell would be complete and the templar would win.
The end result of this dungeon was a failure by my players. No one died, but when the Elemental was bound to the Templar he used its magic to fly off the top of the tower and attack a nearby village. He chose flight as his mission was to recover the magical power to help the Gulg army, and fighting the players would put that power at risk of being taken away from him.
Hope this was an informative post. Any comments, suggestions, or critiques are welcomed. I left this post generally vague so it could be used in any system. If anyone wants specifics such as DCs or Enemy statlines, feel free to voice your opinion and I may change my style later on.