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 of the FAYZ. 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 continue to be fought, although they are outside the FAYZ.