In the desolate wastes of Antarctica, under thick layers of ice and snow, forgotten by the world and only remembered in a few databases of the ancients: There lies Psilabs; a major research complex into the human psyche and the powers of the human mind.
A treacherous door to enter. Take a deep breath, focus your mind, and leap into the ice.
"The wind-driven snow parts for the barest of seconds, revealing a glimpse of refuge from the deadly storm. It’s a massive sapphire pyramid. Yet you know of nothing like it in this area…"
In the trackless Frozen Waste, at the heart of the Sra lands lies the sacred glacier Ganamed, wherein lies Illyana’s Palace, the great ice necropolis of the Sra tribe.
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?