I am trying to identify a horror short story/novella I've read in a vampire-themed Italian anthology in the mid 2000s. The story was probably much older and written by a British or American author, but I don't have a precise time frame.
The basic premise was that a nobleman (or a member of middle/high societal class) invited his peers to his mansion, only to show them that there is a huge, dark cave habitat right under it, which he decides to explore and use as a hunting ground. The setting was around the beginning of 1900, or so I seem to remember.
I recall the nobleman in question dying alone, at the hand of a pitch-black monster inhabiting the cave and his story being passed on to his peers through an audio record that was somehow retrieved in the cave by someone (his aide?). There is also a chance his demise was broadcast through an open radio channel instead, but I am not sure if this is the case.
While in the cave, the characters were wearing some sort of rebreathers and some survival equipment, including firearms - if my mind isn't mixing details from another story
I have queried Google with prompts such as horror story hunting ground cave under mansion -movie -game
and horror story large cave under mansion -movie -game
, to no avail.