White Crane, Black Diamond
Two monks are sent as messengers from the head of their order to the ancient monastery of White Crane Mountain. The night before they arrive, they have bad dreams of a terrifying black light.
Arriving at the monastery, they discover that the monastery is abandoned, with all the monks missing, and no sign of what happened to them.
Eventually, they find a locked door, with the key still in the lock, but on the opposite side of the door.
After getting the key and entering the room, they find the body of a monk, dead from hunger/thirst, manacled to a bed. Scratched into the stone beside him is the word "beneath".
A second key - which fits the lock on the manacles - is in the opposite corner of the room. (the monk came in, locked the door, chained himself up, then threw the key away).
Naturally, the monks probe the depths of the monastery and find a cave network. The start to find the drained husks of the other monks - the corpses are dried out and almost skeletal. A few of the corpses animate and attack, but are easily vanquished.
Eventually, they reach the heart of the caverns, where a pulsing black jewel starts trying to compel them to come closer and touch it. The compulsion isn't strong enough to control them, however (they haven't been exposed for long enough), and so the jewel's guardian, a hideous man-spider cross (use the fang of lolth PrC if you have it, otherwise I could stat something up) attacks them.
The monks eventually vanquish him, and discover the tortured head of the order. He dies as they watch, but his spirit lingers long enough to tell them that they must take the jewel - without touching it with bare skin - to the springs at the heart of the caverns, where it will dissolve in the pure water. They must hurry, however, for the villains that planted the jewel - the head of the Black Diamond Monastery - has already sent fresh agents to stop them.
Cue a harrowing chase through the caverns as ninja attack the two monks, who must survive long enough to immerse the jewel in the spring.
