The Primus extracts a Mixed Yuan Bead into a Spirit Seed and a Demon Pill. The Spirit Seed can be reincarnated as a human to help King Zhou establish a new dynasty, whereas the Demon Pill will create a devil threatening humanity. Ne Zha is the one who is destined to be the hero, but instead he becomes a devil incarnate, because the Spirit Seed and a Demon Pill are switched.
