Palden Lhamo is a wrathful Buddhist goddess derived from the ancient Indian goddess Shridevi.  In Buddhism she became a dharma protector and guardian of the truth (dharmapala).  More than that, she is also considered to be a Buddha, an emanation sent forth from the dharmakaya, expressing the enlightenment energy of a Buddha.  Her main driving force is a vow taken long ago to help and protect those dedicated to the enlightenment path.  Palden Lhamo specifically protects the faith, Lhasa (the capital of Tibet), and the Dalai Lama.  

The flaming sword she wields in her right hand is symbol of her function as a protector of the Buddhist doctrine.  It represents the victory of enlightenment over the attack of the hosts of Mara which are the hindering forces of ignorance.  The scorpion hilt indicates extremely wrathful activity.  Her wrathful nature is further symbolized by the skulls in her crown, the garland of freshly severed heads she wears, the skull cup she holds to her heart in her left hand, and the flayed skins she wears as upper and lower garments.  The animals that surround her are taken from her mandala, which uses animals to represent her.  She is shown here without the mule that she usually rides.