Lord Sri Nrsimha Dev is the incarnation of Supreme Personality of Godhead Sri Krishna. As per Srimad Bhagwatam, he appeared personally from the pillar in order to rescue his dear devotee from the wrath of his father Hiranyakashyipu.
His fearful form terrorises the death itself and it appears that he is the death of the death. His form is so much fearful that no one dared to go near him when he tore apart the demon with his nails. Only his dear devotee approached him and with eyes filled with tears of love and affection for his lord, he fell at his lotus feet and offered prayers.
Similarly, if one offers prayers to Lord Narsimha, then there is no problem in these three worlds from which he can be tormented. Lord is always there to help his devotees and he personally comes and carries whatever his dear devotees lacks and preserves what he has.