Aztec mythology celebrates the serpent god Quetzalcoatl for his role in the world’s creation, but his dog-headed twin brother, Xolotl, is often forgotten—or worse, known as “a monster,” according to the opening of Newbery Medalist Donna Barba Higuera’s Xolo. After a cataclysm that wipes out humanity, the gods descend to Earth so that they may shepherd the eventual resurrection of life.