Lang is an aristocratic clan whose genealogical account Potiseru (po ti bse ru) tells of the clan's mythic and divine origins. The Lang is descended from the Dra clan, one of the four great Tibetan ancestral lineages. Originally from a valley of the Drichu river in Kham, members were active in government from at least the time of Tibet's Yarlung dynasty. Later, the clan would gain prominence in association with the Pakmodru noble house and their monastery Densatil. On the heels of waning Sakya power and the imminent fall of the Yuan dynasty, the Pakmodrupa under Jangchub Gyeltsen gained control of central Tibet in the mid-14th century. In 1618, the Pakmodrupa were defeated by the Tsangpa rulers.