After listening to Pamela's explanation, Corey finally understood why it was extremely important for one to register themselves in a city.
Not only did it help the leaders of a city know who could be a potential threat to the safety of the city, but it also helped them to gain a sort of control over the uncontrollable element called Outsiders.
To Outsiders like him, if he wanted, he could choose to commit mass slaughter since according to The Clown, they would not truly die and they were also not of this world so they had no attachments to this world.
Finding an ancient stone was not easy at all. Take, for example, Corey had killed a herd of Capra Feroxes but not a single one of them dropped an ancient stone.
He had to kill a Temple Guardian and a being that was stronger than an average tier 6 to get an ancient stone.