In keeping with my other 'Underworld' idea, after entering that initial gate, there are actually seven more. This is only the second on the way down, and this party of folks will not make it as far as the exorcist from the first image. So This guard, not only addresses this issue of access to the gate, but is a containment facility all in one for problematic witches and this kind of thing, those who messed with the spirit world in a wreckless way.