There are many superstitions in this book, but don't judge too harshly. Keep in mind all cultures have superstitions. Look at our fear of black cats, Friday the 13th, and breaking mirrors, to name a few! Okonkwo commits a great sin when he beats his wife during Peace Week (Chap.4); it is believed that evil will fall upon the whole clan, so he must atone. They also believe if a child is stillborn, it is ogbanje,a wicked child who, when it died, would enter the mother's womb again to be reborn (Chap.9). Such children would be mutilated by the medicine man and dragged off to the Evil Forest to discourage them from trying to be born again. Since Ezinma is thought to be obanje, though she has lived, she is always sick, so another superstition is to dig up her iya-wa,the stone which is the link between Ezinma and the spirit world. They also believe in Ogbu-agali-odu, an evil essence loosed upon the world through secret medicines (Chap.11). They believe the priestess, Chielo, can commune with the gods and spirits. There are many more superstitions, yet I would say the most important involves Okonkwo's exile; that is, when his gun goes off, and he commits a female crime, he is exiled to his mother's land for seven years. This banishment begins the inevitable destruction of Okonkwo and the natives' way of life.
on top of those, we have some more peculiar ones, such as not whistling at night for fear of evil spirits, and calling a snake a string, because if they called it a snake, it would hear.