Aditi!

Aditi, meaning limitless is considered as the mother of all the celestial gods.

She is the mother of Adityas(the devas) and wife of Rishi Kashyapa. Aditi herself is considered as the divine wisdom, the goddess of space, consciousness, the past, the future, and fertility. In fact she is also considered as the female Brahma, the creator.
When the devas lost their kingdom to king Bali, the powerful 'Danava', Vishnu was born to Aditi as Vamana avatar to defeat the powerful Bali and restore the lost kingdom to devas and make Indra the king of Devalok.

Source:
http://en.wikipedia.org/wiki/Aditi
http://www.webonautics.com/mythology/avataar_vamana.html