Question: Could you explain who is Shyamala Devi?
Shyamala Devi is the form of Durga Devi who assists Lord Krishna in interacting with the material world during His incarnation (as Shyama). For every incarnation of Krishna or Narayana there is a form of Durga that assists Him to interact with the material energy. Narayana is nirguna, He does not have any connection with the three modes of material nature. As such He is always aloof to matter and never comes in contact with it. When He desires to interact with the material energy He does so through a via medium. It is like using a spoon to stir a pot of soup. We don’t stick our hand into the soup and stir it, we use a via medium, in this case the spoon, to do it.
In the creation and manifestation of the material nature, the Maha Vishnu uses the assistance of Shambu to impregnate the matter with the living entities. Shambu is the utensil He uses to touch the material energy.
When the Lord incarnates, a similar situation occurs. The Lord’s body is absolutely spiritual, but He is interacting with elements from the material energy. For example, when the Varaha avatara wanted to lift the Earth planet, a form of Durga named Varahi came in between and actually lifted the Earth. The Earth is material, but Varaha was purely spiritual. As such they were, in a sense, not compatible. To harmonize the interaction, Durga assumes a form and carries out the will of Narayana on the material side, thus He remains nirguna – not having come in contact with the material energy. It is because of this that some Puranas describe the same story leaving out the incarnation of Narayana. They may say Durga took the form of Narasimhi and killed Hiranyakashipu. It is not false, she did take that form, and she did perform the action on the material side of existence, but they are leaving out the complete story. This is why Durga is called as the chaya-shakti, or shadow energy. She acts as the shadow of Narayana. In the words of the Gita:
“The material energy is functioning under My direction.”
There is a Bengali text called Chandi (Chandi Mangala, not Chandi Path) which among other things describes the various forms of Durga in relation to the forms of Vishnu. Much later Devi Bhagavatam was written, but it has become more popular now, since Chandi is written only in Bengali.