Warriors (book series)
The cats live in five groups called Clans: ThunderClan, RiverClan, WindClan, ShadowClan, and SkyClan. When Clan cats die, they go to StarClan (Heaven) or the Dark Forest/Place of No Stars (Hell). The first mini-series, the first two books of the second mini-series, and the fifth mini-series are set in a forest that the authors have said was based on the New Forest area of England. The rest of the second mini-series and the third, fourth, sixth, seventh, and eighth mini-series are set in a different forest that surrounds a lake.