Mileena is a clone of Kitana, created by Shang Tsung's sorcery in his flesh pits for Shao Kahn, using Tarkatan physiology. Vicious and evil, she despises Kitana, and feels that it is her own right to rule Edenia as Princess in her place. Her fondest wish is to kill her "sister", and claim her existence for her own. Something of an opportunist, she will make use of any chance to seize power that comes within her hands.
Originally, as with all MK female ninjas, Mileena wore a tight bodysuit (and mask), with her uniform being colored in shades of magenta. Later on, her costumes changed, some of them rather loose, but usually more revealing than Kitana's. In terms of physical features, she is identical to Kitana except her face, as her visage is twisted by the Tarkatan DNA flowing in her veins, giving her a large mouth rimmed with long, sharp teeth and and orange sharp eyes much like Baraka.
In Deception, she compensates for this by wearing revealing apparel to show off more of her lascivious physique, wearing a veil to keep her face hidden.
In Mortal Kombat (2011), she boasts an even more revealing outfit, much like her alternate costume in Deception and her eyes are Tarkatan-like. In Kitana's part of the Story Mode, Mileena's appearance when Kitana encounters her in Shang Tsung's Flesh Pits showed Mileena with Tarkatan teeth and wearing nothing but bandages on parts of her body giving a half-naked appearance.