overview
Warriors is a series of children's novels published by HarperCollins. The series is published under the pseudonym Erin Hunter and writing alternates between authors Kate Cary, Cherith Baldry, and Tui Sutherland, with plot ideas by editor Victoria Holmes. The series follows the adventures of four Clans of wild cats in their forest homes. The four Clans are ThunderClan, WindClan, ShadowClan and RiverClan. After death, most of the spirits of Clan cats join StarClan.It stated that there were originally many small groups of wild cats who lived in the forest. Without a code of honor to follow or ancestors to provide guidance, they constantly fought for food and territory. One night, at Fourtrees (a group of four tall trees), a large battle occurred, and many cats died. The spirits of the cats killed in battle returned and told the cats to "unite or die." Thus, four cats, Thunder, River, Shadow, Wind (and possibly a fifth cat, Sky), came forward to become the leaders of the first Clans, ThunderClan, RiverClan, ShadowClan, WindClan, and SkyClan. The dead spirits became StarClan, and slowly, the warrior code was created as described in Code of the Clans.
The warrior code is a code of honor that all warriors are taught when they are apprentices, and must follow. The warrior code is understood to contain many individual rules, however, they have never been all mentioned. The warrior code includes rules on loyalty, territory, prey, processes involving specific members of the Clan (ex. "a kit must be at least six moons old to become an apprentice"), and battles.
*explanation courtesy of wikipedia