Dark Forest is where evil, villianous cats like Tigerstar go once death is upon them. Dark Forest (Like StarClan) can visit cat's in their dreams, and are known to train young, strong cats fighting moves. Almost every cat trained by Dark Forest is suspected by their Clan-mates, due to the fact DF trains battle moves from all four clans. Meaning that the cat may attempt a move during training, and spill their cover. Dark Forest has been at war with Star Clan since the begining of the clans. Not physical battles, but wars between living cats and secret training for young apprentices. Starclan has tried to put a stop to such training, but Dark forest grows stronger when Starclan is weaker.
"A great battle is coming, ready your warriors for battle, sharpen your claws. Because by midnight, most of these cats who stand before you will be dead."-Molepelt
