Lord Vishnu follows his first mammalian incarnation of Varaha with that of Narasimha, who is half-lion and half-human. When the evil king Hiranyakashipu tries to kill his own son, Prahlada, as a result of his false pride and fury over Prahlada’s devotion to Vishnu, the Lord incarnates in his most aggressive form to save his favorite kid devotee. Because Hiranyakashipu has already challenged Prahlada to prove that his Lord (Vishnu) pervades all materials, including a pillar in their courtroom, Narasimha appears out of the pillar and destroys the evil king using his nails as a weapon.
After this event, Narasimha arranges another short divine play: His fuming anger becomes uncontrollable and starts shaking the world. To make things worse, worship by all the gods fails to appease him. Finally, on Narada’s advice, Prahlada surrenders himself at Narasimha’s feet. On seeing his devotee, as the Srimad Bhagavad Purana tells us, he eliminates his fabricated anger and blesses Prahlada with instantaneous awakening.
Besides teaching that the Lord is omnipresent and protective, this incarnation demonstrates that the Divine rates pure love from the jiva higher than worship by even devatas, who are his own manifestations. This appearance of Vishnu is solely for a devotee.
In astrological language, the Narasimha incarnation is correlated with Mars, which, being the most aggressive planet, matches Narasimha’s image who has intense anger on his face and blood on his nails but still fights for dharma. Once dharma is established and Narasimha calms down, he depicts the pleased and protective side of Mars, which acts as a benefic in the horoscopes of beings who have taken the refuge of righteousness.