Morrígan

Winter Goddess (冬の女神 Fuyu no megami): is one of the old gods of Winter and Death.

Appearance
As the mother, the Winter Goddess is a tall woman with exceptionally long, dark and wavy hair with a motherly figure. Her eyes are bright with white pupils. She's clad in a long that reaches down to her feet, it's black from the ankles and upwards while the lower parts are white.

As the daughter, her appearance takes a stark contrast to her mother as she's a small child with white hair and a shorter dress. Her eyes have a black sclera while her iris remains bright and the pupils are white.

Personality
The mother comes off as a stoic and serious being while being presented in a regal presence, yet her demeanor changes somewhat when she takes notice of a branch from an oak mistletoe. As she takes ahold of it, her mood becomes much happier.

The Winter Goddess clearly appreciates gifts as it's later shown as the daughter pays Ruth back for the glistening dews and branches that he gave to her mother in the form of lending out her flame. Much like their appearance, the daughter takes on a more gentle and playful nature compared to that of her mother, as can be seen when she smiled at a clearly frightened Ruth.

Background
The Winter Goddess is first mentioned just before the night of Yule, an important cycle of the year that showcases the shift between the winter and the coming spring, by the Twins of Yule and later by Elias. The Winter Goddess later seen riding on top of another god, it's revealed that she's pregnant as she unknowingly passes by Elise, Chise and Ruth. Before leaving she takes notice and picks up a mistletoe.

The Winter Goddess later appears again before Ruth as he searches for Chise, being first mistaken to be the Slay Vega before Ruth gets a closer look at her and sees a resemblance between her and the Winter Goddess from earlier, quickly deducing that this must be her daughter. The Winter Goddess learns that Ruth had offered gifts to her mother, the mistletoe, and as thanks, she decides to help him by lending Ruth her "flame", which reveals Elias position to him. Ruth says thank you before leaving to find Chise, the Winter Goddess replies only that next winter, when she's her mother, she asks only for that which Ruth offered her then.

Skills and Abilities
As an old god, the full extent of the Winter Goddess's powers are unknown but she's known to hold power over the world of winter. Being called a god of both winter and death, it's suspected that she holds some sort of powers related to both of these realms and humans have celebrated and made offerings for her coming during the night of Yule, even since the times of old. As such, she's feared by even individuals such as Elias.

Spells
The Winter Goddess has been seen lending Ruth her "flame", which allows the Winter Goddess to light up the surrounding area to such an extent that she's able to reveal vasts parts of the forest and even reveal the location of others. As was shown when she revealed the location of Elias and Chise to Ruth.

The Deer
Whether their relationship is that of friends or that of servant and mistress is unknown. They're both referred to as gods and while they haven't been seen exchanging words with one another, their presence together and the fact that she's riding him towards their destination suggests that they're on good terms and that they hold some level of trust for one another.

Trivia

 * The concept of the Winter Goddess is a slight alteration of the Goddess of Yule, a being that becomes the Great Mother before giving birth to the new Sun Goddess.