Narasimha is the most fierce avatar of Lord Vishnu.He broke Hiranyakashipu's neck like a twig and clawed his stomach ,screaming in extreme delight,all because the demon king had forbidden his son,Prahlad from worshipping Vishnu and was trying to murder him.
As Narasimha's anger crossed the limits and was causing harm to the nature,the Devas prayed to the Goddess Lakshmi ,the beloved wife of Vishnu, who in turn,prayed to Lord Shiva,to pacify the anger of her husband.
Soon ,Lord Shiva appeared and had a war with Narasimha,thus,making him realise his real-self.Both Lord Narasimha and Lakshmi then appeared before Prahlad,who sang a praise for them ,on being encouraged by Lord Brahma,for so ,doing.
But the anger of Narasimha did not disappear fully even after that,and he started wandering in the forests.Therefore, Devi Lakshmi took the form of a tribal beauty,Chenchu Lakshmi, who made the ferocious Narasimha to fall in love with her.Chenchu Lakshmi did tapasya to make Narasimha's anger fade-away.
Lord Narasimha soon realised ,that the beautiful lady is none other than,his own divine wife, Devi Lakshmi, so,they got married amidst of great celebrations made by the Chenchu tribe.
Lord Narasimha,the most ferocious form of Lord Vishnu,appeared handsome beside the beautiful Lakshmi,whom he made to sit upon his left thigh,and this murthy of the Lord with Lakshmi,is the most auspicious form of Lord Narasimha.