Manasa - the Snake Goddess - Hydra Origin

 Once, when serpents and reptiles had created chaos on the earth, sage Kashyapa  by Meditating on Lord Shiva and Durga created goddess Manasa from his mind (mana). 

The creator god Brahma made her the presiding deity of snakes and reptiles- gaining control over the earth

Manasa wanted to become worshipful propitiated her Spiritual Parents Shiva Durga, who told her to please Krishna(Original Vishnu) which she did by chanting Sri Shesha Shayi Namah(Mantra) . 

Upon being pleased, Krishna appeared before  her and gave her divine Siddhi powers and ritual worship making her an established goddess.

Manasa / Devi / About / Youtube 

http://en.wikipedia.org/wiki/Manasa 
https://en.wikipedia.org/wiki/Mangal-K%C4%81vya

http://mansadevi.nic.in/ 

http://hinduism.about.com/od/hindugoddesses/a/manasa.htm

https://www.youtube.com/results?q=manasa+devi 

Husband

https://www.google.com/search?q=Jaratkaru

Son Astika who prevented snake sacrifice of Janmejaya
http://emp8.blogspot.com/search/label/Successor

Popular Name Hydra is Inspired By This  Goddess
http://en.wikipedia.org/wiki/Hydra_(disambiguation) 
https://www.youtube.com/results?search_query=Hydra 

Raksha Bandhan 
https://www.google.com/search?q=Devi+Manasa+Tying+Rakhi+to+Lord+Ganesh