Are there other Brahmas and universes?
Chapter III On seeing the Devî of Devi Bhagavatam says, there are multiple Brahmas, multiple Vishnus and multiple Rudras.
After killing Dânavas Madhu Kaitabha, three deities got into a beautiful Vimana sent by Devi Bhagavathi. They saw multiple Satyaloka, multiple Vishnuloka and multiple Kailasa.
Brahma said this to his son Narada,
Then the car, where we were situated, began to get up high in the sky, and in the twinkling of an eye, we reached Brahmâ loka, that is saluted by all the Devas. There S'ambhu and Kes'ava were greatly bewildered to see Brahmâ of that place. In the council hall of Brahmâ, the Vedas with their Angas, the serpents, hills, oceans and rivers were seen. Seeing all these, Visnu and Mahes'vara asked me :-- “O Four-faced one! Who is this eternal Brahmâ? I replied :-- I do not know who is this Brahmâ? Who am I? and who is He? why has this error come over me? You, too, also are gods so you can better ponder over it.” Next our car, going with the swiftness of mind went, in the twinkling of an eye, to the beautiful all auspicious Kailâs'a mountain surrounded by bliss-giving Yaksas. It was beautified by the Mandâra garden, resonated by the sweet cooings of S'ukas and cuckoos and the sweet sounds of lutes and small drums and tabors. When we reached there we saw the five faced, three-eyed Bhagavân S'ashi S'ekhara, with ten hands, wearing tiger skin, and the upper garment of the elephant skin. He was then, getting out of his abode, riding on a bull. His two sons, the great heroes, Ganes'a and Kârtikeya, beautifully adorned, were attending Him as His body guards. Nandi and all other hosts were following Him, chanting victories to Him. O Muni Narâda! we were greatly wondered to see another S'ankara, surrounded by the Matrikâs. So much so, that perplexed with doubts, I sat down there. Next our aeroplane went on with the force of wind; and in an instant reached the abode of Vaikuntha, the amusement court of Laksmî. O Sûta! There at Vaikuntha, we saw a wonderful manifestation of power. Our companion Visnu was greatly surprised to see that excellent city. We saw there four-armed Visnu, of the colour of Âtasi flower, wearing yellow garments, adorned with divine ornaments sitting on Garuda. Laksmî Devî is fanning wonderful chowry to Him. Struck with wonder at the sight of the eternal Visnu, we took our seat on the car and looked at one another's face.
Besides this, "Concept of multiple Brahmandas" is described in Chapter 10 "Shiva Swallowing Poison" of Skanda Purana (Pg- 78).
This chapter says
He (Ganesha) saw crores of spherical Cosmic Eggs like so many atoms. They were getting merged and dissolved in Mahesha who was in linga form.
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