Amnion nodosum is frequently also present (nodules on the fetal surface of the amnion). The chorion and the amnion together form the amniotic sac. The trophoblast layer differentiates into amnion and the chorion, which then comprise the fetal membranes. The chorion functions to separate the amnion from the maternal decidua and uterus. An amnion, chorion, and allantois are present during embryonic life. The amniotic cavity is surrounded by a membrane, called the amnion. The amnion is characterised by cuboidal and columnar epithelial layers. The fusion of the amnion and chorion is completed at the 12th week of development. The somatic layer depends on a continuous layer with mesoderm that covers the amnion. Amphibians and fish are not amniotes and thus lack the amnion. The forewaters are released when the amnion ruptures. According to Herodotus, Cambyses' campaigns against Amnion and Ethiopia ended catastrophically. He tells the monster that he has the Splinter of Amnion. The hypoblast is pushed out of the way and goes on to form the amnion. After defeating the Amnion, Alex finds Joshua's corpse inside the monster's body.