Key to the Ages

Generations ago, in a time long forgotten, there were four Artefacts. First first was a staff, imbuded with the power to bring anything it touched to ruin. The second was its counterpart, an amulet that gave shape to thoughts of the wearer. The third to be fashioned was a simple book, gifted the entirety of all knowledge of all things or all time; nothing was hidden from those who read. The last Artefact was a miniscule key, whose rotation caused time to move backwards and forward, and even become undone. These four Artefacts were meant to stop all wars. They did not. Instead, the gods who gave power to these watched in horror as the four relics ripped the world apart. After endless years, these same gods created four beings, one to wield each relic, and a fifth who could not wield any of them to watch over the world, and ultimately undo their failure. Each of these beings was reincarnated upon their deaths, and each given incredible powers with each new life. It took many years, and countless generations, but eventually, these beings succeeded. The Artefacts were seemingly destroyed sixty years ago, in a blast of magic that was felt across the multiverse. Now, we join a small group of heroes who have stumbled across the strangest thing: a city, stuck in looped time. But, why?   DM's Note: For anyone who may wander into this world, my players have now completed two games, both of which were introductory. They know none of the above history (ahahaha!), nor into what they are walking.