Limbo

You CANNOT leave this place, thoug you may teleport into it. Limbo is often used as a way to completly seal away someone with literally no opportunity escape. Limbo is a place of eternal limboes where one cannot cast spells or attack others in any way. One is also completly secluded from others, and cannot make contact.
Limbo is not a plane of any alignment. But has a place in The great wheel.