Cinderkit was born to Sorreltail and Brackenfur towards the end of Twilight. She is formerly introduced after the badger attack, and Squirrelflight let's out a shocked squeak at the resemblance between the tiny kit and the former medicine cat, Cinderpelt. In Sunset, Leafpool discovers that she is indeed a recarnation of Cinderpelt, when Spottedleaf tells her where to find Cinderpelt and shows her Cinderkit. Cinderheart is not consciously aware of her situation and is very much her own character, though her personality is similar to Cinderpelt's before she was injured; Jayfeather's attempts to walk in her dreams result in the personality of the original Cinderpelt revealing herself in the former ThunderClan camp in the forest, implying that Cinderpelt's spirit does indeed reside within Cinderheart's subconsciousness. Leafpool and Jayfeather are the only cats that are aware of Cinderheart's true identity; while Leafpool wants to keep it a secret from Cinderheart indefinitely, Jayfeather wants to reveal the truth to her, thus adding heat to the already obvious indifferences of these two cats..
She and Lionblaze become close during Fading Echoes, and Night Whispers. She and Lionblaze seemed to be deeply in love, but Cinderheart breaks the relationship when Lionblaze tells her that he is part of the prophecy. She tells him that they can't be mates, and as a result, she breaks Lionblaze's heart.
Cinderheart is StarClan's answer to Cinderpelt's dreams of becoming a warrior. She becomes an apprentice under Cloudtail along with Jayfeather, Lionblaze and Hollyleaf, her best friend, and others. In an ironic twist of fate, however, she falls from a tree branch in Dark River and injures her leg. She is able to recover partially, but reinjures it during her assessment in Eclipse and is very distressed about it, thinking her sisters will become warriors before her. Jayfeather teaches her to swim in order to stretch and build the muscles without putting weight on them, and by the end of Eclipse, Cinderpaw is able to walk and run normally and receives her warrior name, Cinderheart.
At the end of Eclipse, when she is given her warrior name, Firestar names her Cinderheart, "...in honor of those warriors who have gone before.", referring to Cinderpelt.
During Sunrise, Honeyfern dies, and Cinderheart is grief-stricken. She tells Hollyleaf she shouldn't have said anything at the Gathering. In "Omen of the Stars", Cinderheart is Ivypaw's mentor, and trains her along side Lionblaze and Dovepaw.