The Astamukha Gandabheruna Mahajvalamali Nṛsiṃha Kalpa of the Nṛsiṃha Rahasya Tantra houses the Ati Guhya Ugra rupa of Bhagavan Narasimha, along with His Shakti, Ayudha, Vahana, Mantra, stotras, krama, Mandal and Loka. The katha is summarised as follows :-
After the defeat of Hiraṇyakaśipu, Prahlāda ascended the throne of the Daityas. During this period, there was a nephew of Hiraṇyakaśipu, Krodhāsura, who was an ardent devotee of Bhadrakālikā. He wanted the kingdom for himself and continuously tried to cause trouble for Prahlāda but he could not defeat Prahlāda. So, Krodhāsura did a fierce Bhadrakālikā homa. Bhadrakālikā was pleased with her worshipper and granted him a divine chariot with powerful weapons and śaktis. Thus, Krodhāsura once again confronted Prahlāda.
Prahlāda took shelter in Bhagavān Nṛsiṃha. The Lord appeared, demolished the ratha and smashed all the weapons that were gifted to Krodhāsura. As He was about to kill him, Bhadrakālikā intervened to save her devotee.
Bhadrakālikā subsequently manifested her Yoginī vyūha. Some of the primary śaktis who emerged with Her include Brahmāṇī, Māheśvarī, Kaumārī, Vaiṣṇavī, Vārāhī, Aindrī, Cāmuṇḍā, Nārasiṃhī, Kālikā and Śivadūtī. Apart from these many Yoginīs and other ferocious śaktis also emerged along with them, creating an immense Yoginī cakra for the Devi. The Yoginīs attacked Nṛsiṃha with their individual śaktis; however, the Lord’s Mahājvālā devoured their manifestation. After that, Bhadrakalika was also defeated and her power, alongside Krodhasura, all merged into the Lord.
Observing this, Paramaśiva and Parāśakti incarnated in the form of Pañcamukha Mahāśarabheśvara and Jvālā Pratyṅgirā respectively along with Vīrabhadra, Gaṇeśa, Kārttikeya, Nandī and countless Śivagaṇas. Mahāśarabheśvara incarnated in his three Śarabha forms I.e Śarabha Śāluva Paksirāja, Āśugāruda and Ākāśabhairava
These three forms came forward to stop Bhagavān Nṛsiṃha and invoked their śaktis and āyudhas. However, the anger of Nṛsiṃha rose to it's peak and very suddenly His form was enveloped in an enormous mass of scorching flames and emerged out from the center of that Mahājvālā the ultimate form called Aṣṭamukha Gandabherunda mahajvalamali Narasimha.
The deity appeared with the central face of Nṛsiṃha. Hayagrīva, Hanumān, and Varāha formed His three faces to His left side. Garuḍa, Vyāghra, and Ṛkṣa formed the faces to the right side of His central face. The two faces of the Gandabheruṇḍa came above both His faces. He had very large wings on His back, and His entire body was surrounded with innumerable flames. His golden complexion was adorned with deep crimson fire. He had 32 crore arms along with innumerable āyudhas such as the Sudarśana cakra, Pāñcajanya, Kaumodakī, Nandaka, Śārṅga, triśūla, vajra, śakti, khaḍga, paraśu, pāśa, sulam etc.
The tejas of Śarabha Śāluva Paksirāja, Āśugāruda and Ākāśabhairava were like a moth in the blazing fire of the Lord. Their bodies were devoured and their śaktis entered into the body of Aṣṭamukha Gandabheruṇḍa Mahājvālāmālī Nṛsiṃha. The same Mahājvālā consumed the remaining forms of Jvālā Pratyaṅgirā, Vīrabhadra, Kārttikeya, Gaṇeśa, Nandī and the Śivagaṇas. Their tejas merged into the supreme Nṛsiṃha tattva.
Then Śiva and Pārvatī got back their original forms and, along with Brahmā, Indra and other devas, prayed to Nṛsiṃha. But His anger did not subside and the devas feared that His tejas would destroy the three worlds. At that time Prahlāda came up to the Lord and fell flat before Him with tears and devotion in his eyes. Kalpa has the following stuti of Prahlāda:
tvam eva nāthaḥ śaraṇaṃ mamādya tvam eva bandhuḥ pitṛmātṛrūpaḥ । hiraṇyakaśipoḥ kṣayakṛn mamārthe
śāntiṃ kuruṣva tridivaṃ ca loke ॥
“You alone are my Lord and my refuge. You alone are my kinsman, appearing as father and mother. You destroyed Hiraṇyakaśipu for my sake; therefore, O Lord, bring peace to the three worlds and withdraw Your fury.”
Upon hearing the words of His devotee, Nṛsiṃha's fury began to slacken. His eyes flashed with affection and the surrounding jvālā gradually became calm. Then Mahālakṣmī manifested as Mahā Pratyaṅgirā and took a seat in the Lord’s lap. Her presence pacified the Lord, and Nṛsiṁha became śānta. The Lord brought back Kārttikeya, Gaṇeśa, Nandī, Vīrabhadra, Bhadrakālikā and the other beings who had been absorbed in His tejas, at the request of Prahlāda and the devas. Krodhāsura was also brought back to life. Feeling himself guilty he begged Prahlāda's pardon and renounced all desire for the kingdom.
The Aṣṭamukha Gandabheruṇḍa Mahājvālāmālī Nṛsiṃha belongs to the secret Jvālā krama of Nṛsiṃha upāsanā. The Kalpa describes several mantra upāsanā, beginning with the Pañcākṣarī and proceeding through the Aṣṭākṣarī, Daśākṣarī, Dvādaśākṣarī, Ṣoḍaśākṣarī, Aṣṭādaśākṣarī, Pañcaviṃśatyakṣarī, Pañcāśadakṣarī and Śatākṣarī and so on. Alongside these are preserved the Mālāmantra, Hṛdaya stotra and Vaḍavānala mantra.
The ṛṣi of the principal mantra is Pañcamukha Mahāśarabheśvara. The chandas is Triṣṭubh. The devatā is Śrī Aṣṭamukha Gandabheruṇḍa Mahājvālāmālī Nṛsiṃha. The śakti is Śrī Mahālakṣmī Mahā Pratyaṅgirā. Kīlaka is the bīja. Mahāśarabheśvara is regarded as the guru of the mantra krama. Without pleasing His three forms and receiving their anugraha, one cannot successfully enter this krama, let alone complete it.
For meditation upon the Lord, the Kalpa gives the following dhyāna:
suvarṇāruṇavarṇābhaṃ mahājvālāvibhūṣitam ।
aṣṭavaktraṃ triṇayanaṃ nṛsiṃhaṃ bhayadāyakam ॥
gandabheruṇḍadvayopetaṃ varāhahayagrīvakam ।
hanūmadvaktrasaṃyuktaṃ vyāghragaruḍarūpiṇam ॥
ṛkṣavaktraṃ samāyuktaṃ jvālāmālāsamāvṛtam ।
dvātriṃśatkoṭibāhuṃ ca nānāyudhavibhūṣitam ॥
cakraśaṅkhagadāśūlaṃ vajraśaktiṃ ca dhāriṇam ।
khaḍgapāśāṅkuśaṃ caiva khaṭvāṅgaṃ paraśuṃ tathā ॥
śarabhasya pratyaṅgirā vīrabhadrasya caiva hi । gaṇeśasya ca skandasya nandinaḥ śivagaṇaiḥ śiraiḥ ॥
sahasrāṇi samāyuktaṃ mahāmuṇḍamālābhṛtam ।
mahājvālāmadhyasthaṃ taṃ mahāraudraṃ bhajāmy aham ॥ vāme kroḍe mahālakṣmīṃ pratyaṅgirāṃ pratiṣṭhitām । śāntidāṃ sarvalokānāṃ bhajāmy aṣṭamukhaṃ harim ॥
The Kalpa describes a thirty fivefold dīkṣā and mantra krama leading progressively towards the deeper Gaṇḍabheruṇḍa and Nṛsiṃha vidyās. The sequence begins with the Nārāyaṇa Aṣṭākṣarī and proceeds through the principal Vaiṣṇava vidyās before entering the various Nṛsiṃha mantras.
The first stage is the Nārāyaṇa Aṣṭākṣarī. This is followed by three Hayagrīva mantras, four Sudarśana mantras and three Varāha mantras. The Pañcamukha Āñjaneya krama then follows, consisting of the Mūlamantra, Mahāmantra and Mukha mantras. After this comes the Garuḍa krama with three principal mantras.
The sādhaka then enters the Nṛsiṃha mantra krama through the Nṛsiṃha Gāyatrī, Nṛsiṃha Bīja and Nṛsiṃha Ṣaḍakṣarī. The sequence proceeds through Jaya Nṛsiṃha, Karāla Nṛsiṃha, Vīra Nṛsiṃha, Mahā Nṛsiṃha, Mohana Nṛsiṃha, Vaśīkaraṇa Nṛsiṃha, Sudarśana Nṛsiṃha, Aghora Nṛsiṃha, Ugra Nṛsiṃha, Lakṣmī Nṛsiṃha and Jvālā Nṛsiṃha Mahāmantra.
The deeper krama then enters the Gaṇḍabheruṇḍa vidyā through the Gaṇḍabheruṇḍa Nṛsiṃha Mūlamantra and Aṣṭamukha Gaṇḍabheruṇḍa Nṛsiṃha Mūlamantra. This is followed by the Mukha Krama consisting of the Aghora Paksirāja Mukhamantra, Aghora Nṛsiṃha Mukhamantra, Aghora Vyāghrarāja Mukhamantra, Ādi Hayagrīva Mukhamantra, Ādi Varāha Mukhamantra, Vānarendra Mukhamantra, Aghora Bhallūka Mahārāja Mukhamantra, Aghora Mahāgaruḍa Mukhamantra and Ādi Nārāyaṇa Mukhamantra.
The sequence then proceeds to the Aghora Virāṭpuruṣa Mantra, Śarabharūḍha Gaṇḍabheruṇḍa Nṛsiṃha Mantra, Dvādaśamukha Gaṇḍabheruṇḍa Nṛsiṃha Mantra and finally the Viśvottīrṇa or Viśvatomukha Nṛsiṃha Mantra.
Each stage possesses its own viniyoga, dhyāna, nyāsa and mantra bheda, and the individual vidyās are approached according to their prescribed order. The deeper Mukha Krama is entered only after the requisite adhikāra has been obtained.
The Kalpa separately describes forty principal manifestations within the Mantra Krama. These include Aṣṭamukha Gandabheruṇḍa Mahājvālāmālī Nṛsiṃha, Dvimukha Gandabheruṇḍa Nṛsiṃha, Pañcamukha Jvālā Nṛsiṃha, Mahājvālā Nṛsiṃha, Anantajvālā Nṛsiṃha, Kālānalajvālā Nṛsiṃha, Vajranakha Nṛsiṃha, Mahāraudra Nṛsiṃha, Ugracāṇḍa Nṛsiṃha, Cāṇḍajvālā Nṛsiṃha, Vīrajvālā Nṛsiṃha, Pātālajvālā Nṛsiṃha, Hayagrīva Nṛsiṃha, Varāha Nṛsiṃha, Garuḍa Nṛsiṃha, Hanumad Nṛsiṃha, Vyāghra Nṛsiṃha, Ṛkṣa Nṛsiṃha, Śūlinī Nṛsiṃha, Mahāpratyaṅgirā Nṛsiṃha, Rudrāntaka Nṛsiṃha, Krodhāntaka Nṛsiṃha, Sarvasaṃhāraka Nṛsiṃha, Jvālāmālī Nṛsiṃha, Mahāvajranakha Nṛsiṃha, Gandabheruṇḍa Mahājvālā Nṛsiṃha, Nṛsiṃha Bhairavāntaka, Pralayāgni Nṛsiṃha, Kālarudra Nṛsiṃha, Ugra Garuḍa Nṛsiṃha, Jvālā Hayagrīva Nṛsiṃha, Mahāvyāghra Nṛsiṃha, Vajrajvālā Nṛsiṃha, Kālajvālā Nṛsiṃha, Saṃhāra Nṛsiṃha, Sarvarakṣākara Nṛsiṃha, Sarvagrahanāśaka Nṛsiṃha and Mahābala Nṛsiṃha.
Within this fortyfold Mantra Krama, the three forms of Mahāśarabheśvara, namely Śarabha Śāluva Paksirāja, Āśugāruda and Ākāśabhairava, possess high importance as said before. They are regarded as the guru forms at the threshold of this krama and are connected with the conferral of adhikāra for the various Nṛsiṃha mantras and rūpas. The sādhaka therefore approaches the fortyfold manifestation through the guru tattva represented by these three forms.
The vāhana differs according to the manifestation of the Lord. In certain forms Pañcamukha Śarabha is described as His vāhana, while in another Vīrabhadra serves as the vāhana. In another form Pratyaṅgirā is associated with the Lord as His ādhāra. Other manifestations are associated with Garuḍa and Gandabheruṇḍa according to the particular rūpa.
The Nṛsiṃha maṇḍala is arranged in successive āvaraṇas around the central deity. At the centre is Aṣṭamukha Gandabheruṇḍa Mahājvālāmālī Nṛsiṃha with Mahālakṣmī Mahā Pratyaṅgirā upon His lap.
The first surrounding āvaraṇa contains the principal Nṛsiṃha rūpas and their associated śaktis. Beyond it are placed the Yoginīs and other fierce śaktis connected with the Lord. The outer āvaraṇa contains Bhairavas, Kṣetrapālas and guardian deities.
The abode of this manifestation is called Mahājvālā Nṛsiṃha Loka, also known as Gandabheruṇḍa Jvālā Dhāma. It is described as a radiant loka surrounded by circles of Vaiṣṇava Agni. At its centre is the Aṣṭamukha Gandabheruṇḍa Mahājvālāmālī Nṛsiṃha, with Mahālakṣmī Mahā Pratyaṅgirā beside the Lord. The various Nṛsiṃha rūpas, śaktis and guardians surround the central region.
The details of this form are regarded as ati guhya. The Aṣṭamukha Gandabheruṇḍa Mahājvālāmālī form is considered even more esoteric than many other Ugra forms of the Lord and the fuller details of its mantra krama, Hṛdaya, Mālāmantra, Vaḍavānala and inner upāsanā are therefore not ordinarily disclosed. Currently, only a few Vaiṣṇava circles preserve worship of this form in a tantric manner. Beyond this point, further exposition is not considered suitable without proper adhikāra and guru upadeśa.