What is the significance of Maa Siddhidatri's worship on Day 9 of Navratri?

Maa Siddhidatri, the ninth form of Goddess Durga, is worshipped on ninth and final day of Navratri. Her name means giver of "siddhis" or spiritual attainments. She symbolises fulfilment and spiritual accomplishment. Traditionally depicted seated on a lotus, she has four hands holding a chakra (discus), shankha (conch), gada (mace) and lotus flower. Some depictions show her riding a lion.