Another Venger Satanis product, this time a location.
I see the title "La Bas Chartreuse", and I expect fin de siècle decadence and Satanism, because, well, Huysmans. As far as literature is considered, I think this offering veers closer to R.E.Howard's "The Black Stone", or Abraham Merritt's "The People of the Pit".
This is not a fleshed-out scenario, but a single location (albeit a location that holds portals to all worlds and dimensions). Presented as a letter from a madman who witnessed its terror; a few pages of descriptions (all non-Euclidean, full of squamous voids and pulsating luminescence, and similar words); and many random tables to give you ideas on what can happen in this place. Useful and plunderable things include a d20 table of "Properties of alien metal" ("Reverberates sub-audible dark ambient vibrations" / "All vegetation nearby turns gray, shriveled, and lifeless" and so forth).
This location can easily be dropped into occult horror investigation games with a pulp or exploitation bent - the author's The Outer Presence, Call of Cthulhu, Kult, etc. (or added to a sword & sorcery campaign). So if you are into this specific flavor or insanity, go ahead.
I like the flavor, although I have a couple of reservations. Mainly, I fear that there's only so many eldritch adjectives and black voids a person (player or game master) can take. Stuff like this quickly becomes repetitive... So, beware, and control your dosage.