It looks like Linden Grecio didn't want anyone to leave. At the same time needed the participation of all in the town to maintain the place. So he turned to an ancient artifact he found to achieve those goals. He used the artifact to create a monstrosity to help maintain the law of the town.The people rebelled later and imprisoned him. His last act was pouring his will and life force into the artifact to curse the citizens of his town that they may never leave the vicinity of the town ever. All the citizens of the town turned into hideously ugly creatures, doomed to remain in their own houses for fear of being mocked by all who see. They didn't dare go back to the Human colony for they are sure they would be attacked on sight. Linden Grecio lived to see his handiwork, before he finally breathed his last. The location of the artifact was currently unknown. It was believed that by breaking the artifact the curse would be lifted.