Three kings meet to negotiate an alliance versus the common foe. That foe employs the services of three witches who curse the kings as they meet. Each king loses his senses save for one, one can still see, one can hear and one can speak, but none can move. The adventurers, preferably one each from each king's bodyguard or retinue, must set out to lift the curse.
The sages and priests can divine (either NPCs or PCs if powerful enough) that no army can meet this threat but that only by blinding, deafening and rendering mute each of the witches will the senses be restored.
The location of the witches must first be divined, and a possible option is: Entering the plane of the gods and requesting a boon from the Fates (Norns) the three crones who weave the fate of all beings, even the gods. They will be able to read the threads of the witches, who they see as somewhat impudent counterparts. The Fates will require three gifts to grant the locations.
1: A ball of thread left by a hero in the maze of a minotaur. Sad to say the minotaur still lives and will challenge the PCs in mortal combat.
2: A golden apple dropped by a goddess when squabbles broke out over who was loveliest. Sad to say the apple has worms, and as a giant apple the worms are giant wyrms. Once recovered the apple will shrink to a normal apple size.
3: The head of a gorgon, left in the desert and now used as a toy by a giant sphinx. the sphinx will, once the authority of the PCs is revealed, only release the gorgon's head after 3 riddles are answered correctly. (see the netbook of riddles). Note this is a gorgon's head, don't look at it.... (Oddly enough it doesn't affect the Sphinx)
The Fates will then divulge the positions of the witches. They will finger the threads of the witches and reveal that the time has not come to cut these threads. They will explain that the adventurers must complete their quest without killing the witches.. They will give the adventurers the thread, the apple and the gorgon's head.
In a flash the PCs will return to the castle, no time having passed, ready to hunt the witches.
Each witch's lair lies three days from the castle and may be visited in any order. The witches are:
Frankel, Witch of Sight
In a tall tower atop a moor, Frankel is guarded by harpies, gargoyles and giant birds. The tower can only be entered from the roof and within it are mirror traps, illusions, mists and other optical trickery. Frankel uses magicks that can create multiple copies of her herself, invisible creatures and spells of light and dark. If Frankel is killed then the Fates will cut the thread of the seeing king and he will die. If Frankel is blinded in some way (and chaining her in a dungeon with the gorgon's head on display would force Frankel to keep her eyes shut....) will restore sight to the two kings who are blind, restore full senses and movement to the seeing king BUT blind him too. (no it's not going to be a totally happy ending is it?)
Josel, Witch of Hearing
In a dark forest Josel is guarded by wolves, boars and howling banshees. Living in a giant tree, Josel will use silence spells, spells of great noise to burst eardrums and giant spiders which creep up on PCs almost silently. She will use ventriloquism, diversions, trumpets and noise to keep the adventurers confused. If Josel is killed the Fates will cut the thread of the speaking king. If her hearing is taken from her (stuff the thread in her ears and tie it to her arms so she cannot remove it?) then hearing will be restored to the two deaf kings, restore full senses and movement to the hearing king BUT deafen him too.
Carnel, Warlock of Hearing
In an amphitheater left by the ancients, Carnel is guarded by mages and wizards who will cast magicks of command and control. The power of the word will be used against the players. The drill is much the same as the others, the apple will fit neatly into Carnel's mouth, and the usual effects will apply to the kings.
Conclusion
The kings will now be restored, although one will be blind, one dumb and one deaf. They will unite to forge an alliance and the struggle against the foe will continue. OR one or more of the kings are dead, and factionalism and disunity may emerge. Either way the witches will eventually get themselves free, (the magical curses will not return) and the adventurers will have three foes not at all happy to let them continue unopposed...
Twists
Of course the Fates may be the witches and the whole thing was a way of moulding heroes and unity. The Fates may or may not continue to ban the deaths of the witches.