StarClan consists of the deceased warrior ancestors of the Clans, living in a spirit form after death. They watch over the living Clan cats, and have no specific leader; this is the place all four Clans live in harmony and coexistence, working together to ensure the wellbeing of the Clans below. They are responsible for sending omens to living cats. Cats are only allowed to join StarClan if they have lived an honourable life and followed the warrior code; some cats who have broken it are allowed to stay as well, as long as they are good at heart and believed what they were doing was in the best interest of their Clan. Those who do not make it into StarClan instead go to the Dark Forest. StarClan cats do not have to be in a Clan at the time of their death to be welcomed here, as long as they left the Clan on relatively good terms.
When a Clan cat dies, it will be guided to StarClan by someone who held a significant role in that cat's life. When a leader loses a life, that life appears in StarClan as a faint copy of the leader that grows stronger with each lost life. However, they are unable to communicate to other StarClan cats even while there; omens will still bring them messages, but aside from that their communication does not begin until the leader loses its final life.
StarClan cats leave starry pawprints, and have eyes that shine like stars; both have frost glittering along with them. Their pelts glow with a strange light that gives them the appearance of having stars in their fur, and carry the scents of all the seasons. Spirits remain in StarClan until they are forgotten by all living and dead cats, over a long period of time, and they have earned their own peace. At that point, they fade to little more than a ghosty image. If a StarClan cat is killed again, it will vanish forever.
Cats in StarClan act as guardians to the living cats in the Clans, guiding them in times of need or warning them of upcoming dangers. They usually prefer to watch over those they were close to, and prefer to stick to their own Clanmates. Occasionally, living cats will visit StarClan in their dreams, but it is rare for a StarClanner to appear in the waking world. Medicine cats are specially bonded to their warrior ancestors, and are the ones who communicate with them the most. At every half moon, the medicine cats and medicine cat apprentices visit the Moonpool to speak with their ancestors and seek advice or learn of future events. This process begins by drinking the water of the Moonpool. Less frequently, leaders will receive messages from StarClan; even more uncommon are warriors, apprentices, and sometimes even Clanless cats receiving these dreams. All Clan cats are meant to give thanks to StarClan after catching prey, for the life that the prey gave to feed the Clan.
It is believed that all ceremonies are supervised by StarClan, and the leader is meant to call upon the Clan's warrior ancestors before promoting a cat (which is done by the power of StarClan). The leader then asks StarClan welcome the cat by its new name. They have the greatest role during leadership ceremonies, giving the new leader nine lives, gifts, and a new name. Each are granted by a single, significant ancestor.
Although some cats question this, it is believed StarClan has some influence over the living world; for example, if a fight breaks out at the Gathering, the moon will be covered by clouds and lightning even if the sky was clear before. In legend, it is believed that StarClan allows cats to reincarnate before the cat reaches Silverpelt.
Once a cat reaches StarClan, it is told about all the territories and restored to the age in which it was happiest. They do not age there, and keep their names at the highest rank they held or would have achieved.
There is always plenty of prey, and cats have no defined tasks; they do what they please, and only tend to act if living cats are suffering. StarClan cats have universal respect for each other, with no defined hierarchy, although cats tend to instinctively respect their former leaders or mentors.
Although StarClan has a border with the Dark Forest (which appears as a wall of mist) it is advised against entering it because one could become unable to escape. However, cats from the Dark Forest cannot enter StarClan.
Lionheart is believed to have said, "We often walk in the dreams of those we watch. Don't be afraid. I know it looks like a land of mist and shadow, but I promise there is enough light to warm the darkest of hearts. From here, we watch over the Clans we have left behind."