In this form, Durga is seated on a lotus and is four-armed. She holds a lotus, mace, discus, and book. In this form Durga removes ignorance and she provides the knowledge to realize Brahman. She is surrounded by Siddhas, Gandharvas, Yakshas, Demons, and Gods who are worshipping her. The Siddhi that she provides is the realization that only she exists. Siddhidayini form of Durga is worshipped on the ninth day of Navaratri. She is the mistress of all achievements and perfections.
History of Siddhidayini
When the Universal Mother was gripped with the idea of projecting Creation, She, first of all, created Lord Shiva who prayed to Her to endow him with perfections. For this purpose, the Universal Mother (Durga) produced Goddess Siddhidaatri from Her own person. At the behest of the Universal Mother, Goddess Siddidaatri bestowed eighteen kinds of rare perfections and powers and potentialities (Siddhis) on Lord Shiva. By virtue of these siddhis, Lord Shiva happened to develop a divine splendor.
Having acquired the siddhis from Goddess Siddhidaatri, Lord Shiva created Lord Vishnu who in turn created Lord Brahma who was entrusted with the task of the Creation whereas Lord Vishnu got the task of Protection and Lord Shiva that of Destruction.
Lord Brahma felt great difficulty in his task of the Creation in the absence of man and woman. Thereupon he remembered Mother Siddhidaatri. When she appeared before him, Lord Brahma said to her, “Oh Great Mother! I cannot carry on with the task of creation in the absence of man and woman. You kindly solve this problem of mine through your supernatural attainments (siddhis).”
Having heard Lord Brahma, Mother Siddidaatri converted half the person of Lord Shiva into a woman. Thus Lord Shiva became half-male and half-female and came to be known as Ardhanaarishwara. Thus the problem of Lord Brahma was resolved and the task of creation went on smoothly.
Mother Siddhidaatri possesses four arms and she rides on a lion. She carries the mace, lotus, conch-shell, and disc in her four hands. He who acquires her grace attains salvation after enjoying the pleasures of life. She fulfills all the mundane and divine aspirations of her devotees. Her worship destroys all distresses.
Mantras for Siddhidayini Devi
Om Devi Siddhidatryayi Namah (108 Recitation of Siddhidatri Mantra)
Siddha Gandharva Yakshdyairasurairamarairapi | Sevyamaanaa Sadabhuyaat Siddhida Siddhidayini ||
This means, Goddess Siddhidatri who is worshipped by Siddha, Gandharva, Yaksha, Gods, Demons, etc., holds Conch, Chakra, Gada, and Lotus in her hands, giver of all siddhis and victory all over, be propitious to me.
Devotees worship Goddess Siddhidatri on the ninth day of Navratri because she gives the results of nine days of worship.