Recently while reading Prasthana Bheda of Madhusudan Sarasvati, I found he mentioned four forms of Vishnu according to Pancharatra:
Quoting from sanskritdocuments.org:
एवं वैष्णवं नारदादिभिः कृतं पञ्चरात्रम् । तत्र वासुदेवसंकर्षणप्रद्युम्नानिरुद्धाश्चत्वारः पदार्था निरूपिताः । भगवान्वासुदेवः सर्वकारणं परमेश्वरः । तस्मादुत्पद्यते संकर्षणाख्यो जीवः । तस्मान्मनः प्रद्युम्नस्तस्मादनिरुद्धोऽहंकारः । सर्वे चैते भगवतो वासुदेवस्यैवांशभूताः । तदभिन्ना एवेति भगवतो वासुदेवस्य मनोवाक्कायवृत्तिभिराराधनं कृत्वा कृतकृत्यो भवतीत्यादि च निरूपितम् ।
pancarAtram, the vaiShNava shAstram, was composed by nArada and others. In it four entities, vAsudeva, sankarShaNa, pradyumna and aniruddha are mentioned. bhagavAn vAsudeva is the supreme Lord and the cause of everything. From Him emanates the jIva known as sankarShaNa. From him pradyumna, the mind. From him emanates ahamkAra known as aniruddha. All these are part - incarnations of Lord vAsudeva Himself and non - different from Him and so it is said that one becomes fulfilled by devoting the mind, speech and body to the worship of bhagavAn vAsudeva.
Though the work of Madhusudana Sarasvati describe a bit what those four forms are, I want to know and understand from the Pancharatra texts. Besides, while discussing with Keshav Srinivasan, I found that the four forms mentioned by Madhusudana Sarasvati are actually part of one category of forms called Vyuha and the other categories of forms are Para, Vibhava, Antaryami, and Archa.
Hence, I want to know what are the various forms of Vishnu according to Pancharatra? (Quote Pancharatra texts in your answer)