Came across this interesting article on Mantra & Spiritual evolution - Glad to share...
A Dev is the energy responsible for a particular phenomenon of nature. As you progress in yogic practices (Sanatan Kriya), these energies are revealed to you.
Not only do they exist but they actually interact with you and aid your evolution process.
Evolution is moving to a dimension that is higher than your current state. In the etheric world, it is moving from a grosser to a subtler dimension. With relation to your etheric double, it is moving from your basic chakra upwards. This upward movement happens through the etheric reflection of your spinal cord called the sushumna nadi. We know that a strong and supple spine is a prerequisite for yog.
Each of these Devas reside in the etheric portion relevant to every vertebra. For instance, the tail bone in the spinal cord corresponds to the location of mooladhar chakra and is the seat of Lord Ganesha, the energy closest to the physical and of great importance in removing obstacles in the physical world. Evolution too starts from the base of the spine upwards; hence, one has to go to Lord Ganesha for blessings for the journey beyond.