A staff of great power in the hands off those who manipulate the strands of fate.
The Seven Lords of the Peninsulari each wore a magical signet ring identifying them as a sovereign lord.
Most feared of the Regalia of Dominion, the Ruby Sceptre is a terrifying weapon in the hands of a skilled fire mage.
A legendary relic, suited to base a campaign around, with the power of Creation crystallized in a single milky seed…
The shattered remnants of a divine weapon, a certain amount of power remains in these bits of celestial metal.
The finest creations of the gemsmith Sinnameron, the Stones somehow always manage to find their way to the proper people.
Nobody knows how many were made or who the creator was. It is only known that in need, the blades always appear to those that are worthy. They lift those they choose into places of power and use that influence to rage a millennium old war.
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?