About Siddhidatri
In her ninth and final form, Goddess Durga is known as Siddhidatri — 'the Bestower of Siddhis (spiritual accomplishments)'. As her name suggests, she grants all manner of attainments to her devotees. Her form is divine and exquisitely beautiful, adorned with priceless jewels, seated upon a lotus or a lion. She has four arms, holding a chakra, mace, conch and lotus flower. According to the Markandeya Purana, she bestows the eight classic siddhis — Anima, Mahima, Garima, Laghima, Prapti, Prakamya, Ishitva and Vashitva — for there is nothing in the universe beyond the reach of Goddess Siddhidatri's grace.
According to the Devi Bhagavata Purana, it was by her grace that Lord Shiva himself attained all accomplishments, and through this came to be worshipped in his Ardhanarishvara form — half Shiva, half Shakti. Across the three worlds, it is said that Yakshas, sages, humans, demons and gods alike attain spiritual accomplishment only through the grace of Goddess Siddhidatri.
The ninth day of Navratri is dedicated to her; she is worshipped on this final date and holds the last position among the nine forms of Navadurga. Through her, devotees are believed to be able to overcome the entire universe, with all cosmic and spiritual aspirations fulfilled.