The foundation of all the demigods is Lord Viṣṇu, who lives and is worshiped wherever there are religious principles, traditional culture, the Vedas, cows, brāhmaṇas, austerities, and sacrifices with proper remuneration.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
मूलं हि विष्णुर्देवानां यत्र धर्मः सनातनः । तस्य च ब्रह्मगोविप्रास्तपो यज्ञाः सदक्षिणाः
mūlaṃ hi viṣṇurdevānāṃ yatra dharmaḥ sanātanaḥ | tasya ca brahmagoviprāstapo yajñāḥ sadakṣiṇāḥ
SB 10.4.39