Simple Rock image - Obelisk

Welcome to Newbathe, a mysterious town where once a year an event takes place in which demonic creatures scour the lands, for reasons unknown. You, being an Outsider, are kidnapped by an organization to set things right. You are tasked with the goal of building a spire-like object known as the Obelisk. You don't know what it does, or why it must be built, but you will do it. You need to.