 Eventually after the establishment of Namgyal dynasty in Sikkim and under the Lho-Mehn-Tsong Tsum, a treaty between the Bhutia, Lepcha and Limbu people of the Sikkim area, Limbuwan lost the area between Kunchenjunga range (present day eastern border of Nepal) and Teesta River to the Bhutia Kings of Sikkim.Since then Limbuwan comprises all the area between Arun River and Koshi River in the west to Kunchenjunga Mountains and Mechi River in the east.In the beginning of the 15th century, the descendants of King Sirijonga became weak and Limbuwan again fell into chaos and anarchy.