The Censorate was a highly effective agency during the Mongol Yuan dynasty (1271–1368).
The investigating censors were "the eyes and ears" of the emperor and checked administrators at each level to prevent corruption and malfeasance, a common feature of that period.
Popular stories told of righteous censors revealing corruption as well as censors who accepted bribes.
Generally speaking, they were feared and disliked, and had to move around constantly to perform their duties.