Human Rules:
1. Humans MUST be of a reasonable age.
2. Humans may be witches, sorcerers/sorceresses and, as such, may possess various powers. But don't be stupid with it!
3. They must possess physical weaknesses. Being human, the standard weaknesses do apply. Such as starvation, dehydration, poisons, cuts and scrapes, and mortal wounds. If you want to, you can add in things like a weak heart, cancer, an addled brain or brain injury, missing limbs, uncontrollable fear of supernatural beings or even bugs, and even allergies.
5. Humans may carry guns in here. Hunters especially. But no uzi's or mini-uzi's or crap like that. We're a post-apocalyptic time frame here so most of those will not have survived a volcanic winter. Humans still have the basic knowledge to create basic guns and rifles, however, so those are not denied to you. You don't have to resort to muskets, though. I'm not that cruel.