The true significance of the main characters Suratha and Samadhi, with whom The Devi Mahatmyam begins and ends, is explained below.
Suratha (a good chariot) and Samadhi (a concentrated or focused mind) cannot serve their true purpose, cannot find true happiness till they meet the sage, Medhas (intellect or insight or knowledge), who can lead them to The Goddess, to The Supreme Self. ‘Medhas’ is another word for ‘buddhi’ or ‘intellect’. As per the Kathopanishad (1. 3. 3) buddhi or medhas is the charioteer.
Now this is a perfect combination. An awakened intellect or awareness, a focused mind capable of deep meditation, a strong and healthy body, together they can easily attain the best.
Under the wise guidance of the sage Medhas, the king Suratha and the merchant Samadhi attain the best knowledge, knowledge of The Goddess, knowing Whom they can the attain best.
Medhas can now raise their awareness from an ordinary, worldly awareness to a higher, Spiritual awareness of The Goddess, The Supreme Self. And this is what happens finally. Eventually at the end of the narrative, the king and the merchant are fully inspired to seek The Goddess. Retiring to the bank of a river, they meditate and worship The Divine Mother devotedly.
After three years The Divine Mother appears to them and Offers each a Boon. Suratha, who has unfinished business, asks for the return of his earthly kingdom, followed by an imperishable kingdom in the next life. The merchant Samadhi, on the other hand, has grown wise and dispassionate. He has become free from worldly attachment. His mind is now fixed only on Supreme Knowledge, The Goddess. So he asks for the Supreme Knowledge that will dissolve the bondage of worldly existence. This is true Samadhi. All other forms of Samadhi are incomplete, save Nirvikalpa Samadhi.