From the introduction:
The characters have heard rumors of an elephant's graveyard in a desert oasis and gone in search of it, or have stumbled across the oasis by accident. The oasis does exist, and elephants are drawn there, eventually to die. Ivory can be found (when tusks are found as a random encounter, it is an elephant carcass with tusks worth 1d6x100gp, weighing 1lb per 4gp value, each live elephant has tusks of this value as well), but watch out for the elephants. The plant life of the oasis is dominated by red musk creepers (similar to yellow musk creepers, except that the flowers specifically target large herbivores rather than humanoids). Elephants and other herbivores (including the party's mounts) are sprayed by the hypnotic pollen and will remain in the oasis, attacking other animals and stomping them into the soil to fertilize the creepers. But only thick-skinned animals like elephants and rhinos last more than one day here, before the inhabitants of the spire get to them.