The many groups of people inside the FAYZ have often clashed, sometimes resulting in battles of huge ferocity, and often many deaths. These are the most significant battles in the series. After the FAYZ, in the Monster trilogy, battles have continued to take place. In the earlier books, the battles are usually between Sam's group and Caine's, but in later novels they learn to put up with each other and they both fight against common enemies - Drake and the Gaiaphage. In the Monster trilogy, battles take place between morphers.