What is Ahobilam?
Ahobilam is a Narasimha Kshetra or temple for Lord Narasimha, the 4th among the Dasavatars (10 incarnations) of Lord Vishnu. It is one of the 108 Divya Desams associated with Vishnu worship and lies in the beautiful and verdant forests of the Nallamalai ranges in the Eastern Ghats. This part is called Sesha Parvata. The river, Bhavanashini, flows through Ahobilam. Ahobilam Temple is in Kurnool district, Andhra Pradesh. Another name for it is Thiru Singavel Kundram. Narasimha is the half-man and half-lion form of Lord Vishnu. It is believed that Lord Narasimha killed the demon, Hiranyakashipu at this place.
The name ‘Ahobilam’ comes from 2 different events. Supposedly, when the Devas (demigods) saw Narasimha killing Hiranyakashipu, they were awe-struck and exclaimed in wonder, "Aho Balam" (What a strength!). Lord Narasimha placed the demon on his lap and tore him into pieces with his sharp claws.
Secondly, Ahobilam means "great cave". It is said that Lord Garuda (the divine eagle and Vishnu’s mount) performed penance in a mountain here for 1000s of years to receive the darshan of the Lord. Pleased with his penance, Narasimha appeared in a cave nearby. The mountain on which Garuda performed penance is called Garudachalam, Garudasailam, and Garudadri.
Lord Narasimha is said to have manifested here in 9 different forms or "Nava Narasimha" due to Garuda’s penance and other spiritual events. The temple is also associated with the penances of Lord Parashurama, Lord Hanuman, etc. The story goes that Lord Narasimha himself took the form of an old man and gave sanyasa to Van Satagopa Jeeyar, who was the first Jeeyar of the Ahobila Mutt.
Sacred texts like the Brahmanda Purana, Narasimha Purana, Nalayira Divya Prabandhams, and other scriptures mention Ahobilam. According to the Brahmanda Purana, Ahobilam was the abode of Hiranyakashipu.
Ahobilam has 9 temples where the self-manifested forms of the deity are housed. The 9 forms are Jwala Narasimha, Ahobila Narasimha, Krodha Narasimha, Malola Narasimha, Bhargava Narasimha, Karanja Narasimha, Yoga Narasimha, Chatravata Narasimha, and Pavana Narasimha.
There is a popular Sloka in praise of Lord Narasimha that is attributed to the Devas: Ahoviryam Ahosauryam Ahobahu Parakramah | Narasimham Param Daivam Ahobilam Ahobalam ||

Legends behind Ahobilam

Lord Narasimha and Hiranyakashipu
Lord Narasimha killed the demon, Hiranyakashipu, the father of Prahlad, at Ahobilam. Supposedly, the Jwala Narasimha Temple of Ahobilam is where Narasimha killed him. Higher up is a pillar-shaped rock, Ugra Stambham. Narasimha is said to have manifested from that pillar and killed the demon. Lord Narasimha and Garuda

As per Ahobilam Kaifiyat, Garuda performed silent penance inside a cave in a mountain in this area, hoping to obtain the darshan of Lord Narasimha. After several years, the Lord manifested in another cave, and he appeared in a vision to Garuda. Garuda went to that cave and had the darshan of Sri Jwala Narasimha, the fierce form of the Lord who killed Hiranyakashipu. Garuda worshipped the Divya Mangala idol of Narasimha with several Stotras.

Narasimha and Parashurama
Lord Parashurama (an avatar of Vishnu), or Bhargava Rama, also did penance at Ahobilam. The Bhargava Narasimha Temple here is where Parashurama did penance. There is a tank known as Bhargava Tirtha or Akshaya Tirtha near the temple. Lord Narasimha and Hanuman

Lord Hanuman did penance under a Karanja tree at Ahobilam in order to get the darshan of Lord Rama (also a Vishnu avatar). The Lord first appeared as Narasimha. When Hanuman insisted on getting the darshan of Rama, the Lord assumed a form in which he held a bow in his hand (like Rama).

The Karanja Narasimha Temple of Ahobilam is where Hanuman did penance. Narasimha is depicted in a meditative posture with a cobra’s hood over his head. The idol has 4 hands. In the upper right hand, he has the Sudarshan Chakra. In the upper left hand, he holds the Saranga bow. The lower hands show Dhyana mudra. 
Lord Narasimha and the Gandharvas
Two Gandharvas (celestial musicians), Haha and Huhu, came from Mount Meru and sang melodious songs before Narasimha, and he blessed them. Due to his blessings, they became famous singers in all three worlds. The Chatravata Narasimha Temple of Ahobilam is where Narasimha blessed the Gandharvas. Devotees who come here often sing songs to invoke his blessings. The temple is near a Vata (banyan) tree, which forms an umbrella (Chatra). So he got the name, Chatravata Narasimha.

Lord Narasimha and Prahlada
Lord Narasimha supposedly taught several yogic postures to Prahlada here. Lord Yoga Narasimha is depicted sitting cross-legged with a yoga strap around his legs. The Bhagavat Purana talks about how Lord Vishnu came down to earth and taught Prahlad the art of Bhakti Yoga, which gave him invincibility against the demonic powers of his father, Hiranyakashipu.

Benefits of Worshipping Nava Narasimha
Many devotees perform Nava Narasimha Homa and chant Nava Narasimha Mantras to invoke the Lord’s blessings. It protects one from enemies, bestows courage to overcome problems in life, and also helps achieve success in all endeavors.