“ 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.”
“ Shadows, Mirrors and Flames. Three things we have all seen and not given much thought to. What if in each of these things you could find entire alternate planes of existance? Shadows move but what they are shadowing does not. Mirrors show us what others can easily see. Flames dance and twirl inviting you to dance only to scorch you when you get close. These three things hold much mystery. What if you could harness their powers? Heh...”
“ The players encounter an organization dedicated to toppling tyrannous governments; both good and evil. Secretly, they are led by the twin daughters of Lucifer / The Lightbringer / (Generic Adversary God). These daughters have an appropriate set of divine or demonic powers, but strictly speaking, are not evil.”