Hubert submitted this

When you have an annoying little creature that you'd love to kill put it in the torture chamber and torture it to death. It will return as a powerful creature, the ghost. It rises at the level that the creature was. It can still be trained of coarse. Good creatures to kill are spiders, flys, and beetles. But they will not rise as skeletons if you put them in prison. Only enemy prisoners will do that.

Cheap imps? How?