You cannot do that! (Spoiler)
You simply can't leave us viewers not know what happened to Barbara behind the Lizzard door.
It just ain't right..
It was apparent and evident to me that she was doing S & M porn. The black salamander has occult connotations; namely, black magick and sex magick - of which sadomasochism can fall into.
The conversation she has with Oliver Zoco (Oz, as in the Wizard) when she first meets him and before walking through the first door, explains exploring our dark sides. He speaks to her of bullfighting and uses it to illustrate the struggle between reason and emotion and how we should do well to accept our base instincts and to gain control over them, lest they destroy us. This theme carries over throughout the whole film.
This is an excellent film. We need more films like this. Very cathartic.