Used to describe something that undergoes many transformations or variations, as seen in the phrase 女大十八变 nǚ​dà​shí​bā​biàn regarding a young woman's changing appearance during puberty

The eighteen changes or steps involving the manipulation of yarrow stalks required to form a hexagram for divination in the "I Ching"

The eighteen miraculous transformations performed by Buddhas or advanced beings in Buddhist tradition