Excellent, will take a look. I think there is a monster which is as dark as the dark potion as well, but I cannot recall what it was.

As an aside, there is a handy command built into unnethack which doesn't appear in vanilla which I thought might be worth mentioning. It is particularly helpful on a small screen, where one might have to scroll around a level in order to see everything.

The command is #overview - it gives an outline of all the notable features discovered so far level by level, such as fountains, shops, entrance to the mines and so on.