Otherworldly gateways began to appear on all continents. Some furiously elemental, some of ancient carvings. All indestructible. Doorways to different places in another place and time. There was a pressure escaping for days before even a machine could enter the doorways, and then the pressure switched and the air near the gateway began to pull. Nothing ever returned. There was a strange stillness in the world as if something that had been set in machination long ago was about to snap into place.