Hiranyaksha with his power made the earth to lose its vitality and sink into the rasatala (patala). Vishnu assumed the form of a boar (Varaha) and restored earth to its normal position and killed Hiranyaksha.
Hiranyaksha’s brother Hiranyakashipu vowed to seek revenge, did penance and received a boon from Brahma which made him invulnerable to death either in the morning or the night, and either by a human or a beast. Then Vishnu assumed the form of Narasimha avatar (mixed form of man and beast) and kills Hiranyakashipu at the junction of day and night.The earliest inscription at the temple belongs to 1087 CE which mentions about a gift by a private individual in the era of Chola king Kulottunga I. In the later half of the 13th century, the temple complex underwent lot of changes during the reign of the Eastern Ganga king Narasimhadeva I.
An inscription dated 1293 CE refers to the addition of sub shrines by the Ganga Kings in the temple, which were dedicated to manifestations of Vishnu: Vaikunthanatha, Yagnavaraha, and Madhavadevara. NarahariTirtha, a Dvaita philosopher and Eastern Ganga minister converted the Simhachalam temple into a renowned educational establishment and a religious centre for Vaishnavism.The temple received patronage from Reddy dynasty, Gajapathi Kings and many other royal families, of which Tuluva dynasty of Vijayanagara Empire is a notable one. During his military campaigns at the Kalinga region, Krishnadevaraya erected a Jayastambha (pillar of victory) at Simhachalam.The Tuluva kings patronized Simhachalamtemple up to 16th century CE. The temple underwent 40 years of religious inactivity from 1564 to 1604 CE that coincides with the Muslim invasion in the region.