The "Warriors" universe centres around a large group of feral cats who initially reside in a forest, and later, around a lake after fleeing their forest home due to its destruction by Twolegs (humans). The cats are split into five groups called Clans: ThunderClan lives in woodland areas, WindClan resides on the moors, RiverClan by the river, and ShadowClan within and around the swamps. SkyClan, a subsequently introduced fifth group, is revealed to have been a part of this system but was forced to flee when their territory was destroyed by humans for urban development. They rejoined the other Clans during the sixth arc. Each Clan has adapted to their own terrain. For example, RiverClan cats, swim in the river to catch fish, while the majority of cats from the other Clans fear and avoid bodies of water. On the other hand, WindClan cats are faster runners, allowing them to catch rabbits and hares on the open moors of their territory. Relationships between different Clans are usually tense and they often come into conflict with one another. However, the Clans also sometimes show concern for each other; the idea of one Clan being destroyed usually causes deep distress and prompts urgent action on behalf of all Clans.