“ 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?”
“ What if you send the players in a dungeon that was already raided? Maybe you could have traps that are already set off, or the corpses of monsters etc.”
“ One of the camels in the caravan trips over a dark rock protruding from the sandy dunes. The poor animal has broken its leg and cannot continue. A cacaphony ensues as the animal suffers and the caravan train overseers complain passionately as they redistribute the animal's load across the caravan. (Let's just hope none of the PC's was riding this camel, shall we?)
As the camel is put out of its misery and the camel is skewered over a campfire - waste nothing! - someone takes a minute to inspect the root cause of all the trouble. To their surprise, the upturned rock is worked stone. Some frantic digging may excavate the bottom half of a gorgeously worked1 obelisk, and maybe even the small square forum below; but a more rigorous exploration of the surrounding dunes reveals a buried tomb doorway on each side of the forum.”