The term, Marichi's pose, comes from the fact that it is dedicated to the sage, Marichi, from Hindu mythology who is also the son of Brahma.
Marichi's pose D is good for the back, like all twists, because it helps to improve spinal flexibility and brings circulation to the spine. The main twist should occur through the thoracic spine, not the lumbar spine, in order to avoid injury to the lower back.
This pose can relieve back and hip pain. It also stimulates the abdominal muscles and organs, relieving constipation and other digestive issues. The lotus position of the one leg helps to open the hips. It is also helpful for building a core of strength and support.
Marichi's pose D can be performed with a belt between the hands to allow the hands to reach, or without clasping at all. Care should be taken not to twist the knee in attempting to enter this pose and to allow the body to open up over time.