A mandala is a cosmic diagram
Used as an aid in meditation.

The central deity
Represents Durga
In her manifestation
As Mahishusuramordiai,
Slayer of the buffalo demon.

She stands triumphant,
With her 18 arms
Brandishing various weapons,
While dispatching with trident
The demon Mahisha.

The lotus petals surrounding her
Contain the 8 Mother Goddesses.
The Hindu Triad,
Shiva The Destroyer (on the bull Nandi),
Brama The Creator (on swanlike Hansa),
And Vishnu The Preserver (on half giant, half eagle Garuda),
Surmounts the mandala.
The gods are flanked by
Surya (the sun, on left)
And Chandra (the moon, on right).
The rest of the planetary deities are shown below.
 

Don't mess with her.