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.
When the campfires grow dim, stories are told. Stories of lost cities, great heroes and legends of old. One of these is the story of Knurlheim. Once the proud capital of the Dwarfs, now a ruin- abandoned long ago. Filled with vast riches and treasure. It’s secrets forgotten with the decline of the Dwarfs, long ago. No one knows is certain if it ever exsisted at all.