The Mountain of the Ancestors (SB)

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The shamans teach that the ancestors live on the top of a high mountain in the center of the tribe's traditional lands. No one—not even the shamans—is allowed up to the summit, and anyone caught trying to break this taboo is executed.
The shamans are allowed to trek halfway up the mountain, and they do this only to contact the ancestors, offer sacrifice, lead the spirit of a deceased tribesman to the ancestors, and bury the chieftains. While the remains of common members of the tribe are deposited in the funeral grounds on the plains, the bodies of the chiefs are taken halfway up the mountain and left on wooden biers. So, the slopes halfway up the mountain are dotted with rotting scaffolds and human bones where the remains of past chiefs have been deposited. At the same level, animals' bones lie scattered around, the remains of sacrifices made here and left for the spirits, and the mountain supports a small colony of carrion birds (said by the tribesmen to be messengers of the ancestors, bringing news of the living to the dead).
On the Prime Material Plane, the mountain top is a barren, desolate place, but in the spirit world it teams with life. The bulk of the ancestors are found here at all times, and 70% of the time all are present. They can be contacted—by spell, sacrifice or the Medium proficiency—from the boundary of bones on the mountain side, and attempts to communicate with or sacrifice to them gain a -2 bonus on the mountain side.
Should characters wish to climb the sacred peak past the halfway point, they must make Mountaineering proficiency checks, or a Dexterity check with a -3 penalty; any character who fails the check tumbles down the rockface and takes 3d6 points of damage. (The spirits do not appreciate trespassers, and conspire to make the apparently simple climb quite hazardous.) If the roll is successful, or if characters press on despite their wounds, they reach the mountain top where they may hear ghostly, incomprehensible whispers or catch glimpses of forms when the wind whips up veils of the year-round snow. When they descend, they must make another check (again falling for 3d6 points of damage if they fail), and if they are still alive when they reach the bottom they are badly cursed. Any game they kill or animal they butcher will be rancid and make those who eat it vomit; they will be struck barren or impotent; and any plants that they tend die within a month. This curse is permanent, and cannot be lifted except by a wish spell. No sacrifice or heroic action can make amends for those who trespass on the peak.