Welcome to Uhgramudd, you'll never find a more disgusting, remote, fly-ridden, swampy Hell than this. Get in, kill the Lizards, grab the loot, get out. Simple, right?
This is an introductory low-level adventure I use to get familiar with players I meet online, to see if our play styles clash in any way. So far, it has weeded out a few undesirables and scored a few keepers. I am quite satisfied with the layout and have run it multiple times, with slight variations for level/abilities of the player characters.
After the PCs defeat (or force the rapid retreat of) a villanous necromancer/demon summoner, they discover a book. This book outlines how to summon a demon whose power increases according to the size of the summoning circle used to summon it. And after the PCs examine a map of the country, they find that the layout of the cities and roads match up with the required summoning circle. In fact, the final road that would complete the circle is currently in construction.
With anyone who can find out about the circle and the ritual to summon the demon able to somehow make the final road/line, and destruction of the cities and roads currently in existence out of the question (unless this is an evil campaign- that removes the moral quandary), how are the PCs going to solve this problem?