The great gods are mainly the four original. They represent the four aspects of the One Sacchidananda. Brahma or Sad Brahma is Sat or pure Existence, Vishnu or Maha Vishnu is pure Consciousness, Shiva or param Shiva is chit-tapas or pure Force, Krishna or Anandaghan ghanshyam is Ananda or pure Bliss. They have different names in the Vedas but man has lost contact with them. Each of these gods have several projections from Overmind downwards in different planes wherein their original Divine Power becomes cabined in small channels of occult energies. Still lower down they even change into dark beings and are generally worshipped by the Asuras, like certain forms of Kali whom Ravana and Meghnad had propitiated to get occult powers.
It is not just a question of whom one is worshipping as much as of why one is worshipping. One may worship a great god, but if one is asking for petty things, either the god will not always grant it, or he may simply turn away and what may respond to your prayers is some inferior power of vital domain (which is where the wish fulfilling domain lies). The great gods can see through our intentions and respond only if we are true seekers or genuine bhakta. They are too free to be bound by mechanical formulas and rituals. If the devotees are genuinely seeking a higher good such as true knowledge, Wisdom, freedom from ignorance, true love and bhakti and for some reason gets caught in a web of difficulty or stuck with something he needs, then they may respond and help us through it. But in case we use them as simply wish fulfilling device then they turn away. In such a case even if apparently one is worshipping the same outer form and doing the same ritual what begins to play with the human is some inferior deity. If it is a benevolent deity then it may remain in contact for sometime and though the devotee is happy, what he doesn’t realise is that he is getting more and more stuck in the dense mud of ignorance. The cosmic Law rebounds someday and one looses the gains and suffers much. Besides his spiritual progress gets much delayed. Worse still if the forcd that responds is a malevolent one. In such a case, after hooking the devotee and giving him some instant success, they suddenly leave him or even ruin him after having a little fun. That is why in all traditions man has been adviced not to meddle too much into the occult especially hungry for powers. Approach one of the four main gods with the intent of spiritual progress and all is fine. But turn to them for wish fulfilling and a different and sometimes even a dark and dangerous play may begin.
Affectionately,
Alok Da