When Lord Nityananda returned to Bengal to preach the cult of bhakti, love of Godhead, He began touring all over the country. For two purposes — to spread the cult of bhakti and to defeat and subdue the atheists — Lord Nityananda, the most dedicated devotee of the Lord, moved throughout the country.

Lord Krsna appears in every millennium for two purposes, namely to deliver the devotees and kill the nondevotees. His devotees also have two similar purposes — to preach the bhakti cult of Krsna consciousness and defeat all kinds of agnostics and atheistic demons. Nityananda Prabhu carried out the order of Lord Sri Caitanya Mahaprabhu in this way, and those who strictly follow Nityananda Prabhu perform the same activities.

Srila Prabhupada, Cc. Antya 3.148-149, text & purport