D&D General Effect of infestation

[Tyler Dunn]

I have an elder evil called Veskari the Lord of the Swarm whose apocalyptic sign is an infestation of vermin, big and small. What I want to know is what effect would this have on the campaign world. How many people would die?

 

[J.Quondam]

Potentially, it could be a pretty big fraction of the populace-- as many deaths as your campaign could bear, I imagine.
Plague is borne by things like fleas and mosquitoes. Famine follows locusts and grubs that eat crops. Trees are consumed by types of beetles and caterpillars. Even structures can be destabilized by termites. And that's just pretty mundane stuff, without touching on weird stuff like kaiju-scale praying mantises, or swarms of necrotic centipedes, or screaming spiders with human faces, and whatnot.

 

[Cap'n Kobold]

If you have access to Exploring Eberron, there is the Daelkyr Valaara, the crawling queen. Their lair and environmental effects could be useful.