Legitimacy of the caste system

Muluki Ain imposes the caste system in Nepal in order to incorporate people of different origin and bring them under one umbrella of the caste system. The first categories of Thagadhari, which include Parbate Brahmin and Chhetri, are in the higher categories of hierarchy whereas Brahmins of Terai and Newari Brahmin as per Muluki Ain do not fall under these categories.
Matwali group, enslavable and non-enslavable falls under second categories, which include the people of ethnic origin and Brahmins of Terai and Newari Brahmins. It also includes those people in the non-enslavable group such as Magar, Gurung, Rai, and Limbu etc and enslavable are Tamang, Chepang, Thami etc.
Untouchable are the categories of varnas system in ancient Manu's Code but some people such as Muslims and foreigners as well fall into these categories. Untouchables are divided into Pani nachalne choichoto halnu naparne, (Impure but touchable castes) and Pani nachalne chiochoti halnu parne, (Impure and Untouchable castes).
The creation of sub-castes in Nepal is unique. For instance, the child born of a high-caste father and a low-caste mother was a case of promotion. There were unwritten practices like not defiling and sprinkling water which still exists. Children born from wandering sanyasi fathers and intercaste marital relation also belong to the same category.