Complex sentence: When a mysterious Aztec building materialises in Millennium Park, Tom discovers that it belongs to a brutal futuristic race from an alternate Earth, who worship a sentient computer program that models itself after Quetzalcoatl.
Split into simpler sentences: When a mysterious Aztec building materialises in Millennium Park, Tom discovers that it belongs to a brutal futuristic race from an alternate Earth. These Aztecs worship a sentient computer program that models itself after Quetzalcoatl.