This is the sort of thing I intended BADFM to do. Hit the random button and get inspired.
ONE - The final room of the alien shrine. While appearing to be sunlight filtering through the window in the roof, there is only solid rock (or desert sand) for hundreds of feet, if not miles, above. The picture window is in fact a minor warpgate that only permits light to travel through it is transmitting sunlight from a far distant star, perhaps from the alien civilisation's home solar system.
Research suggests that if all the engraved grooves in the walls are filled with a mix of fat and blood from intelligent species, the Featureless Goddess will come to life and grant the performer of the ritual one (and only) question guaranteed to be answered correctly. If the question cannot be guaranteed to be truthful it is believed that reality will in fact shift to match the answer. Clever PCs may be able to use these unanswerable questions to achieve Wishes.
(For example - When will Bountcrass the Usurper die? Since that is not known, an answer of "in ten years to the day" will change reality - Nothing can make Bountcrass die before that date, nothing can prevent his death on that date).
TWO - A Chaos Warrior of the Cult of The Chimaera of Scorpion and Man. It is of vital spiritual importance to these Chaos Warriors that their mortal remains be fed to the temple scorpions, accordingly cult members will go to any lengths to recover their fallen and return what remains of them to the Feeding Pits in their hidden temple deep in the desert. This is undertaken in the hope that one day the scorpions fed upon such will give birth to their Messiah, a hybrid of Scorpion and Man, the titular Chimaera. Somewhat predictably their temple/dungeon is quite heavy on the Dromopoda theme.
THREE - Cranial Parasite. A small grub that nests and grows within the brain cavity of severed heads that still possess a large degree of their original brain matter. Feeding upon the latent psychic energy within, the grub rapidly grows a size commensurate with the skull, growing tentacles with which to move and interact with it's environment and a large, lamprey-like mouth in the original owners jaw.
It's MO is to fight from ambush, dropping upon it's prey and sucking blood until it's prey is dead. It will then repeatedly vomit it's virulent stomach acids upon the neck of the victim until the head is severed, planting a child grub within the head before looking for new prey.
In regions where the Cranial Parasite is known and feared, most cultures practise cremation to avoid the spread of them.
FOUR - Monsieur Guillotine.
AC5, HD3, Att - 2 fists + charm-like effect, DMG - d4/d4, M12, AL:C, Usual undead immunities. Turn as Wight.
A bizarre magical hybrid of guillotine and animated skeleton. Upon encountering living beings that can be killed by decapitation, Monsieur Guillotine will attack while issuing a strange chanting noise. Each enemy who hears the noise must Save vs Spells each round they remain in earshot of MG or sink to their knees in a fugue-like state, totally unable to defend themselves or take any action.
Once all enemies are in a fugue-like state (and those that resisted are dead or have fled), on each subsequent round a random victim will raise and lay him or herself down in the guillotine (one round to perform). On the next round, the guillotine will descend and slay the victim (no save).
FIVE - Lord Treasure-Stomach. Believed by legend to be a narcissistic Earth Elemental who caught sight of his own reflection in the lake and froze in position unable to tear his eyes away. Furthermore it is believed that such creatures exist on a diet of valuable gems that stay secreted in their stomachs and that should the lake ever be drained Lord Treasure-Stomach will awake in a murderous rage and lay waste to the area. Locals will go to nearly any lengths to avoid the risk of adventurers trying to wake him in order to see if the gem diet legend is true.
SIX - Morkhoon the Death-Writer. First you have to locate this ancient, withered undead beast. Then you have to pay his grim price which he will tell you in staccato hisses of a volume barely audible to the human ear. This price varies by job and probably by whim of Morkhoon. Then he will prick himself and draw his thin, black blood and write the name of your target upon his wall and furthermore your name alongside it. The target will be dead within a year and a day. Morkhoon never fails and your name will be alongside your guilty deed for ever. Morkhoon knows who requested the assassination and will always draw the name of the guilty party - it is no use sending a catspaw or delegate to request your dirty work. Amongst the names of the guilty are those of many Kings and Emperors who thought that slaves, servants and messenger boys would be taking the rap for them.