The tenth century is characterized as the period of fragmentation. In the absence of state-sponsored religious institutions and prohibitions, tantric practice developed and spread in central Tibet. To the northeast, several polities ruled independently during most of the century, with the Tsongkha kingdom gaining dominance beginning in 997. In far west Tibet, the Guge Kings claimed descent from the former Pugyel Kings; they were strong patrons of Buddhism and sought to reinstate the empire. Lha Lama Yeshe O, who ruled Guge until 1040, sponsored an enormous revival of Buddhism, sending Rinchen Zangpo to Kashmir to study Indian Buddhism. Under Yeshe O's sponsorship, Rinchen Zangpo translated vast numbers of canonical and tantric works, introduced innovations to art and medicine, and founded many monasteries, such as Tabo, which is still in operation.