The thirteenth day of the fifth lunar month is the day when General Xie Fan of the Underworld achieved enlightenment. Legend has it that Bai Wuchang (White Impermanence), Xie Bian, wears a hat that says 'See Wealth'; Hei Wuchang (Black Impermanence), Fan Wujiu, wears a hat that says 'See Great Fortune'. Therefore, it is popularly believed that worshipping Black and White Impermanence can attract wealth and bless with great fortune and auspiciousness.
In addition, as the Black and White Impermanence are underworld yin messengers, worshipping them can ward off demons and ghosts.