Kaushiki
Kaushiki is a Hindu goddess, a deity who emerged from the sheath of Parvati. She was emerged from Parvati's cells to defeat the asura brothers Shumbha and Nishumbha, and was also the reason the Matrikas come into existence.
Legends
Puranas
The story of Kaushiki is described in Devi Mahatmyam of Markandeya Purana.The Devi Mahatmyam describes that the goddess Kaushiki appeared from the Sheath of the goddess Parvati’s body when the Devas sang her praises.
Fighting with the Asuras for a long time, Parvati's complexion became dark. One day, as Shiva smiled and called devi ' Kali ' Parvati felt offended. She left saying that 'I am going to do penance to Brahma to change my dark complexion'
In the meantime, Shumbha and Nishumbha expelled the Devas from Swarga. They along with Brahma, came to the Himalayas, seeking Devi's help. Brahma asked her what she was doing such severe tapas for, and Parvati replied that I don't want this dark color that my husband doesn't like.
As they were talking, a divine goddess emerged from Parvati's dark skin, Since emerged from the kosha of Parvati, she was called Kaushiki. After shedding her dark skin, The white fair Parvati was known as 'Gauri'.
Goddess Kaushiki also known as Ambika or Chandika is an incarnation of Mahasaraswati. She has eight hands. Lion is her mount. She went on Himalaya to kill the demon brothers Shumbha and Nishumbha, and was also the reason the Matrika’s came into existence.
The generals Chanda and Munda caught a glimpse of Kaushiki and told Shumbha to marry her. With the help of the Matrikas, who were the feminine forms of the Trimurti consisting of Brahmani, Vaishnavi, and Maheshwari, also Varahi, Narasimhi, Sakti and
her dark form Chamunda
Kaushiki and her forces fought the asuras in a pitched battle in order to vanquish them and restore the natural order.
Shiva Purana associates Kaushiki with Ugratara. It mentions that Kaushiki is also called as Matangi because of her source, that is, Parvati.
Kalika Purana describes Kaushiki as the shakti that was born from the body of Goddess Matangi.
Devi Bhagavata Purana describes Kaushiki as the Shakti that came out from the body of Goddess Parvati, and she is called ‘Kaushiki’ in the beginning of Devi Bhagavata Purana.
As a form of Parvati
In Harivamsa Parva, Goddess Parvati tells that she has killed Shumba and Nishumbha.
शुम्भश्चैव निशुम्भश्च सगणौ सूदितौ मया। प्राणसंशयमापन्ने त्वया मोक्ष्यः स शत्रवे । ४० इत्युक्त्वा पार्वती देवी तत्रैवान्तरधीयत ॥
40 - 41. I have with this club despatched to the abode of Yama
the powerful Shumbha and Nishumbha with all their followers. When your life will be in peril, hurl this club at your enemy'. Saying this goddess Parvati disappeared from that place.
- Harivamsa Parva, Vishnu Parva, Chapter 107
नमः शत्रुविनाशिन्यै नमो गौर्यै शिवप्रिये। नमस्ये शुम्भमथनीं निशुम्भमथनीमपि ॥ ७
8. Salutation unto the goddess who has destroyed our enemies. Salutation unto Gauri the 'darling of Shiva. Salutation unto the goddess who has killed Sumbha and pierced the heart of Nisumbha.
- Harivamsa Parva, Vishnu Parva, Chapter 108
In Shiva Purana, Kaushiki Devi accepts Shiva as her husband. Hence, it associates her with Parvati.
अद्वितीयो महेशानः परब्रह्म सदाशिवः । यत्तत्त्वं न विदुर्वेदा विष्ण्वादीनां च का कथा ॥ ५९>
59. The goddess said: One who is called the unique Maheshan Parabrahma Sadashiv and whom even the Vedas and even Lord Vishnu do not know in essence, I am his subtle nature, so how can I bear someone else as a husband?
-Shiva Purana, Uma Samita, Chapter 47
Matsya Purana too glorify Parvati as Shumba-Mardani.
विषभुजङ्गनिषङ्गविभूषिते गिरिसुते भवतीमहमाश्रये ॥ १२ निगदिता भुवनैरिति चण्डिका जननि शुम्भनिशुम्भनिषूदनी l १६
12 & 16. O daughter of the mountain, adorned with poisonous snakes and arrows, I take shelter of you. O mother, creatures of the worlds call you Chandika, the destroyer of Shumbha and Nishumbha. - Chapter 98
Pancharatra Agamas'
In Lakshmi Tantra, Lakshmi Devi tells Indra that she is the shakti who came out of Gauri as Kaushiki and killed many demons, including Shumbha and Nishumbha.
O Sakra, during the period of Tamasa ,
I, the supreme Mahavidya, was Kaushiki, who sprang from the body of Gauri
to slay all those notorious demons including Shumbha and Nishumbha.
Thereby I rescued the worlds and helped the gods.
O lord of all gods, when worshipped with devotion.
I, the goddess Kaushiki fulfiller of many desires, bestow omniscience.
– Lakshmi Tantra, Pancharatra Agama