Helga is a minor character on Once Upon a Time. She is the middle sister of Ingrid and Gerda. As children, the sisters promised to keep Ingrid's magical powers a secret and to love her unconditionally. However, things took a turn for the worst in adulthood when Ingrid accidentally killed Helga with her powers.
Before the Curse
Helga dies at the hands of her sister, Ingrid. ("The Snow Queen")
As children, Ingrid and her two younger sisters, Helga and Gerda play in the gardens of their castle in Arendelle. They come across a man who attempts to kidnap the latter two, but Ingrid accidentally kills him with ice magic. She fears she's an uncontrollable monster, but her sisters promise to be there for her and they make ribbon bracelets to symbolize their love. Many years later, a ball is held at their castle to find suitors for the girls. As Helga and Gerda prepare themselves, Ingrid reveals she isn't going because of her unstable magic. However, as the ball takes place, Ingrid pays a quick visit to it, but when she sees her sisters having fun, she becomes sad and decides to leave. As she packs her things she's caught by her sisters who persuade her to stay as Gerda has heard of a powerful sorcerer that can help contain magic; it is none other than Rumplestiltskin. They visit Rumple and he gives them a magical urn, which can trap any magical being, in return for their ribbon bracelets, as they're a symbol for love and this makes them tainted with magic. Once they return home, the Duke of Weselton, Helga's suitor, makes a move on Ingrid, but she defends herself with magic. He attempts to lie to Helga about what happened, but she doesn't believe him. A fight breaks out and the Duke makes threats, so Ingrid attempts to stop him with magic. However, Helga gets in the way and she turns to ice before crumbling into pieces. Gerda discovers Ingrid beside their sisters dead frozen body and she begins to fear her. Despite Ingrid's pleas for help, Gerda uses the magic urn to trap her. Gerda then visits Grand Pabbie and asks him to remove everyone in Arendelle's memories of her two sisters. ("The Snow Queen")
A portrait of Helga and her sisters is found. ("Heroes and Villains")
Following Ingrid's death, Elsa is finally able to use her powers in order to take down the ice wall surrounding town; however, some of the Snow Queen's magic remains, and her desire to keep intruders out of Storybrooke has made it so that anyone who leaves cannot return. This disappoints Anna, who wants to go home to Arendelle in order to dethrone Hans, but she's told that walking wouldn't get her there anyway; she needs a portal. Wanting to get rid of Anna, who knows of his plans which ultimately fail, Mr. Gold heads to the sorcerer's house and manages to reverse the spell that brought Ingrid into the land without magic, meaning that a door leading back to Arendelle appears. Elsa, Anna and Kristoff go through it with the intention of bringing back the memories of Ingrid and Helga to the people of the kingdom. Just before Anna's wedding, she reveals to Elsa that she found a portrait of Ingrid, Helga and their mother amidst the things locked away in the East Wing of the palace. They decide to display it in deference to their late family members. ("Heroes and Villains")