Mossheart is a member of ancient ThunderClan.
In Battles of the Clans, when Pearnose, ThunderClan's medicine cat, tells Morningstar that his deputy is sick, it is mentioned that Leafstorm hasn't taken any prey since the birth of Mossheart's kits. As they are talking a ThunderClan warrior, Beechfur, pokes his head into the medicine den, and asks if he should lead a border patrol. He mentions to Morningstar that Mossheart told him that Leafstorm was sick. At this question, Morningstar decides to command his entire Clan to search for prey instead of patrolling the borders.
- Battles of the Clans (First appearance; mentioned only)