These Purāṇas are made just to complete Vedic knowledge, or supplementary addition to the Vedic literature. Because Vedic literature is very difficult to understand, therefore they have been expanded by the Purāṇas for different classes of men. So there are three divisions of the Purāṇas: sattvika Purāṇa, rājasika Purāṇa and tamasika Purāṇa. Sattvika Purāṇa is meant for the higher class of people who are in transcendental knowledge of Brahman, Paramātmā and the Supreme Personality of Godhead. Rājasika Purāṇa are meant for those who are aspiring to have improvement of material condition. And tamasika Purāṇa are meant for those who are in the lowest stage of..., little, just like animal life, and to develop them the Purāṇa is helping them to come to the second and first stage.
So in the Purāṇas there are worship of different demigods. Just like in the tamasika Purāṇa there is description of the worship of goddess Kālī. You have seen perhaps the picture of goddess Kālī, a black female standing with sword and cutting the heads of so many people like that, that picture, goddess Kālī. And animal sacrifice is offered before goddess Kālī. So such kind of worship is mentioned in the tamasika Purāṇa. The purpose of such worship and demigods, several times I have explained to you. So Padma Purāṇa is a sattvika Purāṇa, for men who are in the modes of goodness. So here it said that although in the different Purāṇas there are recommendations for worshiping different kinds of demigods, but at the conclusion it is found that Viṣṇu, the Supreme Lord, He is all in all, all in all. Just like... You have not seen in India. Even there is worship of any other demigod, just like Durgā-pūjā, so even in that paraphernalia of gorgeous worshiping arrangement, when the worship will begin, the first worship is offered to Viṣṇu, Yajñeśvara, because, as it is stated in the Bhagavad-gītā, kāmais tais tair hṛta-jñānāḥ yajante anya-devatāḥ: (BG 7.20) "Those who are mad after material sense gratification, they go and worship other demigods to have some immediate reward." And they get it. But how they get it? That is also stated in the Bhagavad-gītā, mayaiva vihitān hi tān: "They cannot have that reward without My sanction."