मृगेन्द्रागमे नरसिंहः

Source: TW

When Indra, angered by the misdeeds of the one who does Vedādhyayana & drinks sura at the same time (Vṛtra), kills him with foam, afraid of the evil, he resorts to Nārāyaṇa. Pleased by his prayers, Nārāyaṇa appears before him & tells him that he should seek Śrīkaṇṭharudra while wearing his (Viṣṇu’s) nārasim̐ha-kavaca. This gives Indra a Nārasim̐ha-rūpa, adorning which he does dhyāna for a 1000 years. At the end of this period, Indra acquires the divine vision of Śrīkaṇṭharudra & the knowledge of Śrīmat-Kāmika from him, which fulfils all his desires.

Since the knowledge given by Indra to Bharadvāja & other Ṛṣis is the abridgement of the wisdom of Kāmika which he received while adorning the rūpa of Narasim̐ha, this knowledge comes to be known as Śrīman-Mṛgendrāgama.

Thus is it narrated by Śrī-Nārāyaṇakaṇṭha in his Vṛtti on Śrīman-Mṛgendra. This is the significance of Narasim̐ha for a Śaiva-Siddhāntī.

मानसतरङ्गिणीकृत्

the mR^igendra frame myth presents a late survival of the ancient mantra: mR^igo na bhImaH kucharo giriShThAH parAvata A jaganthA parasyAH | which applies to both indra and viShNu;