The Vaishnava faith initiated by Sankardeva is known as Ekasarana Dharma, i.e., devotion to one God. The cardinal features of it are : (i) Sravana Kirtana Dharma : the principle of audition was accepted as a stimulating device for religious devotion, (ii) the Dasya view of life was propounded in the manner Kabir and Tulsidas did, according to which the relation of man to God was like that of a servant to his sovereign. It was not like that of a woman to her beloved as postulated by Mirabai or Surdas. That is why the character of Radha and the "fiery power of unreflecting love" are absent as themes from the general purview of Assamese Vaishnavism. (iv)Literature: its recognized channel of expression was meant to stimulate interest among the general masses of the people, women and illiterates particularly. Thus Vaishnava religion, as a revolt against Brahmanism and Tantrism, was manifested in a religion where theology was made vivid and faith in a loving, personal God for the people propounded. Sankardeva (1449-1569) and Madhavdeva (1489-1596), the two best-known saint-poets of Assam, belong to the later medieval period. With a hitherto unknown reformative and creative zeal he paved the way for ankiya nats (one-act plays), the bargits (the devotional songs) and the verse adaptations of the Bhagavat and The Mahabharat, Shankardev brought about the pan-Indian Vaishnavite movement in this corner of the country raising Assamese literature to the status of a great literature. This literature was enriched further by Madhavdev, the spiritual heir and true follower of Shankardev. His Namghosha, a treatise of philosophical verses, Bhakti-Ratnavali, a versification of Vishnupuri Sannyasi's devotional treatise with the same title, Rajasuya Yajna, a poetical rendering of the Mahabharat episode of the Rajasuya sacrifice of the Pandavs, the ankiya nats and the bargits are invaluable contributions to Assamese literature. Other prominent Vaishnav poets of this period are Ram Saraswati, Ananta Kandali, Shridhar Kandali, Ratnakar Kandali, Kangsari Kavi and Sarbabhaum Bhattacharya. The writings of Shankardev aimed at bringing unity to the society by overcoming racial differences.
The main feature round which the literature of the Vaishnava era revolved was the great Bhakti movement. Vaishnava poet-preachers taught that a life of mere external ritualism without the spirit that is to animate and inspire the outer life is a fraud, Mithyachara, as described by Lord Krishna. Vaishnava literary men have focused their energies on trying to show how the philosophy and tenets of the new faith could be given a simple and beautiful expression. Vaishnava literature found a universal response and appeal.
The literature that sprouted its seed in the subsequent phase, 1650-1826, may be assigned the stature of the post-Vaishnavite literature which included the literature of the Ahom period. Though the same Vaishnavite trend may be said to have continued through the period of Shankardev to the fag-end of the Ahom reign, there were much deviations during the later period. A feeling of weariness pervaded the literary atmosphere following the time of the great Vaishnav poets. Under the auspices of the Ahom kings, against the Vaishnavite literature which was always religious, a new kind of prose literature, secular in nature, emerged the historical literature being in vogue. Yet, with most of the writers, the same underlying creed continued. The language of the Vaishnav period had a conventional form with many words borrowed from outside the region. But in this period, literature in the form of history, brought about a language with it roots in its own soil. This new kind of literature influenced even the writers of the Vaishnav tradition to write some of the biographies in prose like the famous Katha-gurucharit.
The Vaishnava literature of Assam, as in other parts of the country, was based to a great extent on the epics which served as the storehouse of materials for literary works. The Vaishnava poets perfected their language to a standard capable of expressing concisely different shades of thought and feeling, including the highly philosophical ones. It could be tender and moving if the poet was describing death or parting. It could be lucid and easy, if he was describing child-life or tranquillity of nature. It could be rugged, majestic and sullen in the passages concerned with bloodshed, battle or calamity.
Gradually, as religious fervour declined, literary Vaishnava works declined as well. Poets like Sridhar Kandali who followed this "grand line" of poets tried to enliven the dying Vaishnava literary traditions. The age that succeeded was an age marked by a political change ushered in by the hegemony of the Ahoms.
Till the end of the Vaishnava era, the centre of literary activity was in western Assam that was under the hegemony of kings either of Kamatapura, Cooch Behar or Kamarupa. This signified a single political unity. With the decline of these kingdoms and the consolidation of the Ahom political power in eastern Assam, the centre of literary and intellectual activity shifted from the west to the east. The Ahoms got merged in the indigenous population and through their successive rulers built up and established steadily a tradition of literary work of a more utilitarian type.