The nāfuel are definitely the followers of Virūpākṣa (Pāli: Virūpakkha), among the list of 4 Heavenly Kings who guards the western path. They work as guards upon Mount Sumeru, defending the dēvas of Trāyastriṃśa from assaults via the asuras. In some instances, the kings by themselves participated in spiritual ceremonies, https://128.199.208.170/