Within the two afterlives, there is StarClan and there is The Dark Forest. Initially intended where all the bad cats of the territories would go to once they passed, although due to StarClan's elitism it seems to be the place where the majority of cats go to once they pass. Cats who simply didn't make it to StarClan's perfection of good. While there are certainly bad cats here, the majority of the population are just average cats, who lived and have made mistakes.

Although, StarClan cannot erradicate The Dark Forest, for you cannot have one, without the other. The two almost seem like mirrors of one another.