In the dry steppelands, one of their most valuable exports is the dried sap of the Larthorn tree. These ugly plants are covered with vicious thorns, but the locals harvest the golden droplets that ooze from their bark each Autumn. This sap, once dried, is valued for its medicinal properties and as a spice. Since little gold or silver is found in the hinterland, the dried droplets of sap are often used as currency by the locals.
On a location with numerous webs, and at least one big spider, there is a something inside a cocoon. It is humanoid in shape, still moving. If the heroes free it (not before they kill or drive away the spiders), they meet a ... zombie!
The poor zombie wandered the dungeon alone, and tried to kill a big living creature (= a spider). The spider used the usual treatment, even if this victim did not look tasty. The zombie can be easily killed as any other zombie. It got but several doses of spider-poison, so can be something worth if it is extracted. You can mention to a druid or ranger the fact the spider had no poison anymore.