It is the responsibility to defend the family's well-being and existence from all dangers and offenses (be they against the body or the honour).
The mund manifests itself as a disciplinary power upon the members of the family; the tenant of the mund has to watch over the women's chastity and faithfulness to prevent the family honour from being harmed; whether a bride is not a virgin at the time of her departure from the family in the case of chastity, and whether sons are born that are not of the common blood in the case of faithfulness.
It became the responsibility of the closer male relative over non-responsible members of the society, i.e. mostly children and women.
For example, Early Franks were divided into Salians, scattered in tribes dominated by tribal munds, and Ripuarians, that were all comprised under the mund of a king in Cologne, although he wasn't the king of all the Ripuarians, but only their "protector".
This can be seen as an archaic building of the momentum that was eventually to concentrate the coercive power (potestas) and legal violence in the hands of a few, namely the nobles, and later only the monarchs.