How long they carried him through those back tunnels, illuminated only by the flickering of torchlight, he had no idea. Then light seemed to explode when they reached the massive chamber. All around, unbelievably large red crystals captured the light of the flames and seemed to multiply it.
Dorlyanic Crystal is a substance from which the ancient Dorlyans, godling-race of a distant planet, forged their mighty weapons. Weapons made from it cleave the flesh of the supernatural and the extraterrestrial like a hot knife through butter.
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.