Extended post on Power of Prayer part-1, 2. Allegory explained.

Allegory has been used widely throughout history in all forms of art, largely because it can illustrate complex ideas and concepts in a way that are comprehensible to its viewers, readers or listeners. They are used typically or as rhetorical device that convey hidden meaning through symbolic figures, actions, imagery and/or events, which together create the moral, spiritual, or political meaning the author wants to convey.  (This is the description by wikipedia.org).
It has also given a beautiful painting as an example.
^Allegory of Music by Filippino Lippi (between 1475 and 1500): The "Allegory of Music" is a popular theme in painting. Lippi uses symbols popular during theHigh Renaissance, many of which refer to Greek mythology.

I have talked about Goddess as cosmic energy in my post:

Power of Prayer part-1.
Power of prayer part-2
I felt the necessity to elaborate on a few terms I used in that posts.

Allegory has been widely used in "Devi Mahatmyam (glory of goddess.) This text is also known as Durga Mahatmyam. to make ideas simpler.
The whole concept has been weaved into a beautiful story of Cosmic energy, with the three central characters.

The Sanskrit word Durga means a fort, or a place that is protected and thus difficult to reach, here it is compared with ourselves. The projection of the stronger and fiercer side of womanhood is but obvious in the tales surrounding Goddess Durga.  

The inner metaphorical significance of the Devi Mahatmyam

The King, the Merchant and the Sage are as allegories to the Body, Mind and Intellect

The cycle of World (samsara) and its inevitable sufferings goes on as long as man does not realize that it is the Self (Atman) that is the rider and not the body or mind or pseudo-self. Unfortunately we continue to suffer till we realize this. It has three main characters smadhi, king and sage Medhas. 

Samadhi, on the other hand is a merchant (vaishya). The word ‘samadhi’ indicates an integrated or concentrated or focused mind, a mind that is absorbed in meditation (‘sam’: together or integrated; ‘a’: towards; and ‘dha’: to hold). In other words the word ‘samadhi’ denotes a focused or concentrated mind, a mind in meditation

The king and the merchant are archetypal characters. We are all a bit like the king and the merchant. We all share their predicament. At some point of time we all experience suffering, hurt and loss. At times our close friends, relatives, and family members fail us. In spite of our deep hurts we still cling on to our old ways and old associations. We fail to discern. We fail to learn from our past. Instead we simply brood over the past constantly reliving our miseries in the present. The king and the merchant find themselves in the hermitage of a great sage in whose hermitage even wild beasts have successfully tamed themselves of their ferocity. Yet the king and the merchant find it hard to awaken their abilities to discern or be dispassionate. Here again we share their plight. Most of us go to a temple or an ashram or a spiritual retreat or a great saint only to find that the mind is still under the conditioning of the past. We worry about our losses and hurts. It would be good if we could reflect rather than brood over our losses and hurts. This is our predicament. Returning back to the merchant Samadhi, though he had the natural inborn ability to engage his mind in meditation, in single minded pursuit, it did not bring him happiness. Instead the end result was unhappiness. Why? He concentrated on wealth alone. The object of his single minded pursuit was only material wealth. You always get what you pursue with a focused mind.

Thus Suratha (a good chariot) and Samadhi (a concentrated or focused mind) cannot serve their true purpose, cannot find true happiness till they meet the sage Medhas (intellect or insight or knowledge), who can lead them to the Goddess, to the Supreme Self. ‘Medhas’ is another word for ‘buddhi’ or ‘intellect’.

The Divine Mother is our own true being, our inherent divinity and wholeness. Her clashes with the demons symbolize the outward and inward struggles we face daily. The Devi, personified simultaneously as the one supreme Goddess and also the many goddesses, confronts the demons of ahamkara or ego (our mistaken notion of who we are or what we identify ourselves. This tale also denotes our constant battle with duality, good or bad, auspicious, and inauspicious.
And in the end one realizes that we are just part of this one cosmic whole. 

pics. and inputs from web.