The purpose of the preparatory mandala (MT2) was to get the energies moving in you. These subtle mental energies are associated with various centers of your body. We have the medulla, the spinal cord flowing down from the brain, which gives energy to every part of the body: a portion of your brain is flowing down through your spinal column to energize the body.
The various chakras like the Muladhara, the Swadhishthana, the Manipura, Anahata, the Vishuddha, the Ajna, etc., is a system created to help you concentrate and activate these subtle energies. After a year or so of practice with the preparatory mandala discovering the movements of mental energies, we have to stabilize it. The advanced mandala will create that stillness within you in which the movement disappears entirely, and only a deep silence and stillness is created, bringing you an intense feeling of peace and empowering your activity with that deep stillness within