Frostmoth has four other siblings. Beepollen, Scarletstar, Cinder, and Tangerineserene. When they were born, their mother, Cherrybriar, left them in the care of their father Crowstep. They were raised as Shadowclan cats and never got to meet their mother. Crowstep left them in the care of another Queen and never took ownership of them. Tangerine'serene on the other paw, was taken to live with Cherrybriar in Riverclan.

When she turned six moons, she had a desire to get to know her parents. She left Shadowclan alongside Beepollen in search of who their parents were.

Frostmoth and Beepollen spent moons trying to find any word of their parents. They eventually ended up in the woods beyond Thunderclan where they stayed for a while. Too embarrased to return to Shadowclan empty pawed, they decided to join another clan or group.

Once they arrived, Morningstar let them join Thunderclan willingly. Their heriatage was never asked about. Frostmoth became a medicine apprentice in hopes to fix some of the wrong in the world. If she had been given the chance, she would have parented orpahened kits to help them avoid what happened to her. She becomes good friends with Fawnstar, Whitecreek, Bramblepath, Hailwatcher, Mountainpine, Snowmouse and Rainstalk.

Frostmoth develops a good bond with Snowmouse, and it was possible the two of them might've become lovers. Before anything could be done, Snowmouse is accused of murdering Bramblepath. She's exiled and not heard from again.

Frostmoth kept a good relationship with her brother Scarletstar, but the three of them forgot about Cinder. Scarletstar finally offers the Thunderclan cats information about their parents and Frostmoth jumps on the opportunity to meet them. Their journey takes them to the city where they learn Crowstep has taken up residence. He's become the leader of a group of rogues. Though proud of his kits, he doesn't take the time to get to know them. Disheartened, Frostmoth returns to the clans with her brothers. They run into Cinder on the way back. At this point in his life he's been a kittypet since he was young. He decides to join Thunderclan and learn of clan life.

On the road back to the clans, Beepollen has an episode where he loses his mind. He attacks Frostmoth and nearly kills her. Scared for every other cat's life, he decides to leave the clans for a while and join Crowstep's group. Frostmoth has to return to the clans without him. Eventually, she leaves to bring him home and she learns about the fate of Snowmouse, one of Crowsteps' group. It is back in the city she recieves a vision about the fate of the clans.. and how Scarletstar would only continue to kill everyone in his path.

She brings Beepollen home, and Scarletstar asks her to help with the ceremony of their medicine cat, Lambhoof. Excited, she takes the opportunity. However, as soon as the ceremony is finished, Scarletstar attacks her. In his fury to hide his secrets, he kills her.

Frostmoth joins Starclan and is furious with her brother. How could he do this to her? After everything she had gone through to keep a relationship with him? She haunts his every waking moment until she realizes that he's plagued with a dark forest type of possession. She becomes determined to find out the cause and put an end to it. While working towards this goal, she meets Snowmouse in Starclan. The two rekindle their relationship.