Despite being as old and ancient as time itself, La Muerte retains her vision of youth and radiant beauty. She is the only known immortal goddess with flesh made entirely of white sugar candy, with black licorice hair and glowing, multi-colored eyes in shades of gold and red. She wears a red dress decorated with cempasuchil, marigold flowers, with lit white wax candles at the hem of her dress.
She also wears an extremely large, wide-brimmed sombrero bedecked with more lit candles and marigolds (her favorite flower), small skulls, pink-plumed, curly, swirly feathers, and palm leaves.
La Muerte also wears a circular gold locket on a choker, given to her by Xibalba when they first met.
La Muerte is a kind, truthful, sweet, generous goddess whose belief in the goodness and pureness of mortal-kind stems from her own heart, as well as from that of the departed and deceased mortal people who are now her citizens and subjects. She loves and cares for everyone and anyone, no matter what or who they are, and will assist anyone who is need of her help, believing humankind to be completely and entirely pure and good. While La Muerte is also very forgiving towards those who truly want to repent, she is also well known for her weakness for wagers. The only known bad side to her is when someone (i.e. Xibalba) cheats in wagers and bets, making her angry despite her sweet disposition.
La Muerte can teleport to nearby places, leaving flower pellets.
She can also transform in many forms such as Mary (the tour guide lady) and an old woman.
She can levitate, float, appear and disappear.
When she snaps of her fingers, Magical things happen and she can pull someone closer without a touch, which means she might have telekinesis.
In The Book of Life
La Muerte and her husband, Xibalba, have been estranged for over a thousand years. Due to having a previous bet, in which Xibalba cheated, she rules the Land of the Remembered, while he rules the bleak Land of the Forgotten. Upon arriving at San Angel together to observe The Day of the Dead festivities, La Muerte remarks that Xibalba's heart has become as dark and cold as the land he now rules. The two have different ways of valuing human beings, as shown when La Muerte stops Xibalba from 'taking' an old man's life. When Xibalba begs for her to trade lands with him, LaMuerte playfully teases and scolds Xibalba reminding him that he is down there by his own doing. She also says that he "is not the man [she] fell in love with all those centuries ago."
Hoping to distract his wife and make a play for the Land of the Living, Xibalba suggests they make another wager. La Muerte is enraged at first, but accepts the idea of a betting game. This leads them to find Manolo, Joaquin, and Maria playing together. This leads to La Muerte choosing Manolo as her champion and blessing him to always have a good and pure heart. As part of the bet, La Muerte makes her husband promise not to interfere with the affairs of man should he lose the wager. Xibalba agrees and the wager is set.
La Muerte reappears on the day Maria returns to town at the bullfighting arena where she slaps Xibalba for staring at Maria and cheers for Manolo when he appears in the arena. She appears after the fight when Manolo sings and Maria hears his anguished song, observing that the mortal girl was moved by Manolo's words. La Muertw appears again, when Manolo serenades Maria on her balcony.
She is not seen again until Manolo, along with his mother and grandfather, reach the Land of the Forgotten to tell her that Xibalba cheated in their wager. Upon learning of this, La Muerte roars in anger! Xibalba appears, thinking his wife wishes to see him and reconcile. Instead he sees Manolo and his relatives along with his infuriated wife. Learning about Xibalba's whole scheme involving the two-headed snake staff, and the Medal of Everlasting Life, La Muerte along with Carmen and Manolo demand Xibalba assist in bringing Manolo back to life. When he refuses, La Muerte tries to persuade him by calling him "Balby", but when he still refuses she becomes angered until Manolo suggests the alternative of his own bet. Offering up the right to give the Land of the Forgotten to her husband, La Muerte convinces Xibalba to give Manolo a fair chance.
La Muerte watches as Manolo meets his worst fear in the bull arena, and is happy to see him emerge victorious, as is the Candlemaker, and, to some extent, Xibalba. The three of them then give Manolo his life back. Later, the three of them use their powers on The Day of the Dead to bring Manolo's deceased family to help defend the town. After the town is saved and the Medal returned, La Muerte and Xibalba reconcile on the top of the church.
Back in the present day, the Tour guide Lady (Mary) finishes her story and then leads the detention children back out to their bus. Waving goodbye, and saying one of the names of the youngest girl the guide reveals herself to have been La Muerte the entire time with the intention of teaching those children something about living and life.