We learn the mystery behind Satyavati's birth, and hear the painful story of Ani Mandavya, who curses the god Dharma to be born as Vidura.
Suggested Reading:
Hiltebeitel, Alf. Rethinking the Mahabharata: a reader's guide to the education of the dharma king. University of Chicago Press, 2001: 32-91.
Adluri, Vishwa. "Frame Narratives and Forked Beginnings: Or, How to Read the Ådiparvan." Journal of Vaishnava Studies 19.2 (2011): 143-210.
Sullivan, Bruce M. Seer of the Fifth Veda: Kr̥ṣṇa Dvaipāyana Vyāsa in the Mahābhārata. Motilal Banarsidass Publ., 1999.