Here's a basic story arc that just sprang to mind. Feel free to use, abuse, modify or otherwise do with as you see fit.
A gentlemen arrives in town one day seeking guides to the area. He hires the PCs to escort him to a hilltop outside of town, where they discover a few stones and the remnants of an ancient wall here and there. They guy reveals that he was once an adventurer from an ancient age, petrified by a medusa's gaze and only recently un-petrified. This place was once his home town, but in the intervening centuries, his homeland and perhaps even all mention of it has vanished.
He hires the characters to search out places from this old town, finding ruins in various states of repair or occupancy. Perhaps the goblins and orcs dwell within the ruins of these ancient places. The characters begin to bring back relics of these ancient times, inspiring an interest in architecture in the capital.
A trading consortium in the capital wants to corner the market on these emerging artifacts. They have a gnome illusionist go among the orc and goblin camps, posing as a wandering goblin shaman. He is spreading word of a coming age of war in which they will rise to prominence and enslave the humans of the region. At the right time, the consortium plans to manufacture just the right messianic figure to go in, unite the goblins and orcs, and get them to abandon the ruins in a war of conquest. While the orcs and goblins are attacking the humans, the consortium plans to sweep through the ruins and secure the relics therein, allowing them to corner the market.
I love this idea - the old adventurer frozen as a statue for years, perhaps centuries or longer. Thanks!