Mountainstar is a dark brown tabby she-cat with dark blue eyes. She is a main character in Mountainstar's Destiny
|Littermates||Flowerpaw, Blazefire, Galeflight|
|Mate||Crowpelt (formerly), Falconspirit|
|Kit(s)||Splashfeather, Jayflight, Stormheart, Ravenwing|
Mountainkit is born to Firefur, the new ThunderClan deputy, and Lightfeather, a ThunderClan queen, along with her littermates, Flowerkit, Galekit, and Blazekit. StarClan sees great power in her when she is born
Mountainkit and her littermates like to play with Duststorm and Berryfur's kits, Falconkit, Cloudkit, and Featherkit. It is mentioned that she accidentally pushed Cloudkit into some thorns. Lightfeather is worried about Mountainkit. Mountainkit and Falconkit get water for the elders and overheated warriors on a hot day, but Flowerpetal passes out and Willowclaw doesn't let them in her den. Mountainkit and Falconkit go down to the lake to get water, but they are attacked by a fox. ThunderClan warriors save them, but they are confined to the nursery until they become apprentices.
Mountainkit is apprenticed to Mistyflower. She, Blazepaw, and Falconpaw are invited to a gathering. At the gathering, she meets a handsome black ShadowClan apprentice named Crowpaw. She falls in love with him.
Mountainpaw trains hard as an apprentice, but she visits Crowpaw every night. When Mountainpaw nearly drowns in the lake, Falconpaw saves her. Their friendship becomes stronger. Flowerpaw also dies from a posioned thrush. Mossstar comes to Mountainpaw in a dream and tells her that her destiny was to save the clans.
When she becomes a warrior, Mountainheart, Crowpaw recieves his name, too, Crowpelt. Falconspirit and Mountainheart are good friends, but Mountainheart thinks he has a crush on her.
Many disasters happen in thunderClan, such as an avalanche which nearly kills Mountainheart, but Falconspirit saves her again.
Crowpelt wants kits, but Mountainheart says she doesn't want kits with him and doesn't want to see him anymore, becuase she was a loyal ThunderClan warrior. Crowpelt gets angry and attacks Mountainheart, but Falconspirit fights him, telling Crowpelt to leave Mountainheart alone. Falconspirit tells Mountainheart that he loves her and they become mates.
Mountainheart becomes pregnant with Falconspirit's kits. The two are very happy living in ThunderClan. Mountainheart gives birth to Splashkit, Jaykit, Stormkit, and Ravenkit. Sadly, Falconspirit dies in a battle a few days after the birth. Mountainheart is distraught.
Splashpaw, Jaypaw, Stormpaw, and Ravenpaw are apprenticed, and Firefur soon dies from the severly cold weather. Mountainheart becomes the deputy.
As a deputy, a large group of rogues appear and are trying to destroy the clans. Mountainheart new about the rogues for a long time. She tells the clans and they train and fight to protect themselves against the rogues. During the battle, Mountainheart kills the leader of the rogues, saving the clans.
Mountainheart recieves her nine lives after Sparrowstar dies from the battle, becoming Mountainstar. She leads ThunderClan peacefully.