Since the Alternian trolls were sent away to prevent a rebellion, how are the twelve trolls still on Alternia? I think I remember karkat looking out his hive and noticing there's no one around his area or something. I'm sorry i'm confused; thank you so much for this blog and that wonderful brain of yours.

Only the adult trolls were sent away. And when Karkat said there was no one around, he just meant that no one was outside at the moment