As the legend goes by, there was a Kuru King called Parikshit who was cursed by a Rishi and was to die in 7 days. Owing to this curse, he wanted to attain liberation / moksha so he went to Sukhdev Ji. Sukhdev Ji told him that listening to the sacred Bhagwat katha will help you attain moksha and so King Parikshit requested Sukhdev Ji to narrate the sacred katha to him. He patiently heard Shrimad Bhagwat Katha which consists of 12 chapters and 18,000 shloka. It takes about 7 / 8 days for one to complete the narration of the sacred Bhagwat Katha and walk on the path of ultimate liberation.
There are 18 puranas in total - Vishnu purana, Shiv purana, Gita purana, Garud purana etc. Every purana can have a pravachan that imparts ancient vedic wisdom which is eternally relevant regardless of the time of your existence. Purana Pravachan can consist of storytelling, mantras, that can be woven into any format as requested.