Many characters in literature is based on the Snow Queen, for example the White Witch of Narnia
A sorceress of great power, Lumi, better known as the Snow Queen, is the commander of the Emperor's personal guard. While its known that Kay reached Fabletown and his eyes were still under the affect of her broken mirror. Its never been stated what happened to her old nemesis Gerda; Kay's childhood friend. Before she became a cold blooded tyrant, she was once an innocent being and was well loved by her people. If anything, she was only known by Vrumptus, to be somewhat fickle with lovers.
According to Jack Horner, she is one of four sisters, each representing one of the seasons, who jointly ruled four kingdoms with each moving in a yearly cycle to bring the seasons in a predictable manner to their subjects. Lumi was also known to have been naive and good-natured, with a childlike and somewhat gullible personality. That changed after Lumi had a relationship with Jack, mostly through his tricks and repeating lines he had used on other women. He somewhat seduced the innocent Lumi. One day, Lumi became ill as her seasonal change was coming near.
She naively gave her powers to Jack, creating the persona of Jack Frost, trusting him to arrange the transfer of the winter season to the next kingdom in the cycle. Jack immediately ignored her wishes, heading off to seek out new women to seduce and generally misuse the abilities given to him. This left the people blaming Lumi for this, while she unknowningly still rested in bed. Through Vrumptus' advice, Lumi, quickly realized that she wasn't ill. Much to her naive surprise, she was pregnant and most likely the child was Jack's. But she had no time to let it sink in, the people were trying to rally against her, blaming her for Jack's misadventures. With her servant's help, he snuck her out of the castle and she eventually took refuge with one of her sisters.
A year had past and she had birthed a son, and still no word from Jack. Realizing he had used her and had been very unfaithful to her, this turned Lumi cold and molded her into becoming the Snow Queen. Eventually, Lumi's three sisters were able to persuade Jack to return the powers that he'd taken. While Jack is a compulsive liar, casting doubt on some of the details, Lumi took offence at a mention of "Jack Frost" during the War and Pieces story-arc, suggesting that at least some of this backstory is accurate. While Lumi has become cold, she has been shown to have lovers, though nothing committed. She's shown immensely loyal to the Empire and Geppetto.
She was present when Boy Blue cut off the head of the Emperor during the Homelands story-arc and even detected his presence before he revealed himself, but was unable to determine who he was masquerading as and thus prevent his attack. When Blue escaped from captivity, Geppetto swore to send the Snow Queen after him to get revenge. In the Sons of Empire story, she acted as host of the Imperial conference called after Bigby's destruction of the magic grove. At the conference, she set out a four-stage plan for the invasion and destruction of the mundane world, which was generally approved, although she was instructed to make alterations after Pinocchio gave details of the likely response to such an assault.
At the climax of the war between Fabletown and the Empire, as shown in War and Pieces, Lumi was present in the Imperial capital when Briar Rose, the legendary, intentionally activated her curse within the city. Lumi immediately fell asleep with the rest of the population, with the exception of the Emperor. When she fell into slumber, her powers were transmitted to her son, the new Jack Frost. However, he returned them to her shortly afterward, but apparently this was not sufficient to wake her up. Recently, the city was burned to the ground, but not before both Lumi and Sleeping Beauty were carried away, still asleep, by a mysterious cadre of goblins.
The Snow Queen has repeatedly shown a sharp mind and a cunning aptitude. Tall and quite beautiful, she is generally surrounded by an aura of cold, to the extent that it's usually snowing in her vicinity, often to the annoyance of those around her, not that any of them would dare say anything. She is capable of pulling in the winter weather surrounding her if she so chooses, but rarely does so. She commands legions of frost creatures, including giants. She seems to have either always known who the true leader of the Empire was or has known for quite some time, as she has been repeatedly shown as one of Geppetto's closest and most trusted allies.
Lumi is a recurring character in the Fables spin-off series, "Fairest", which focuses on the female characters in greater depth. It is Ali Baba who stumbled upon Briar Rose and the Snow Queen in the middle of a Goblin camp; still under the effects of sleeping curse. He first kissed Lumi, who doesn't respond, and then kissed Briar Rose - who after a few moments awakens from her slumber. Ali Baba and Briar Rose then managed to escape the Goblin camp. After killing and torturing all the goblins, who "dared to put their warty hands on her and dump her in a cart, like a bag of thrash", the Snow Queen, seeking vengeance on Briar Rose for putting her to sleep for years, sends her ice giants after Briar Rose and Ali Baba. Eventually, both are captured and taken to the Snow Queen. Instead of killing them, she forces Briar Rose to tell her the story of her life, as Lumi "is addicted to good stories". It is revealed that Lumi's actions while serving Geppetto was a result of Geppetto putting a spell on her that made her utterly loyal to him. Jonah Panghammer convinces Lumi that she has no real reason to hate or harm Briar Rose, although she was put under the sleep effect of her curse, it makes her realize something. With Geppetto and the Emperor gone, Lumi was no free and her world was safe, she could move on and be happy again.
But before she can go and let Briar go, she's forced to go under a heavy battle with the evil fairy Hadeon the Destroyer (due to Jonah saying her name too many times). After the heated battle, Ali Baba eventually realizes that he has no feelings for Briar Rose after all, but is in love with Lumi. Lumi discovers that she likes and is attracted to Ali Baba, and believes that love can grow from that. The two go back to Lumi's homeland, and start a new life together.
It should be noted that so far, Lumi's not asked or wondered what became of her son. Its also unknown if she will reunite with her sisters or how she'll react to her son's death.