It's the first room of the dungeon...
The usual stone--weathered but basically smooth. Exits wherever you need exits to be.
In the center of the room are three pedestals, made from the same rock as the room. Contents:
On the extreme right, in a small pot, an orchid.
In the center, a goblet, with red wine.
On the left, cake.
This room just freaks the PCs out. Every time. I've run it four times and nobody knows what to do here. You could write the whole rest of the dungeon in the time it takes the PCs to agree on what to do here in Room 1.
What do the flower and the wine and the cake do? It hardly matters--you're a DM, you can make something up if you want to use this room. The real effect is done as soon as you describe the room.
Another thing I notice about this room--thinking about it now--is it is, to me, a very D&D room.
What I mean is, like, though I love Warhammer aesthetics--the skull-crushing and all that--I love how they exploit the metalness latent in D&D that D&D's first creators weren't metal enough to recognize (but its young fans were)--but you wouldn't expect to see a room like this in a Warhammer FRP game. Maybe not consciously, but you just wouldn't put it in. (Probably, yes, I know you had this DM once who...but you get my point.)
Early D&D had a stamp of...not "whimsical", exactly, because "whimsical" sucks (and D&D had sucky whimsy sometimes too, and it was a different thing)...it had a stamp of...I guess I'd call it a sort of uncategorizeably puzzly weirdness. Probably left to it by Jack Vance and fairy tales (and Lewis Carroll, who left a Jabberwock for early Warhammer). In Warhammer (especially later) the weirdness was Chaos and Chaos would kill you sooner or later--in other words, the awesome metalness of Warhammer--the certainty and "focus" of its aesthetic direction--can make it predictable. The same goes for other "focused" medieval variants--Ars Magica. If you walked into a dungeon and saw a cake and a goblet and an orchid in an Ars Magica game you wouldn't bat an eye. It wouldn't be fun, it'd be some standard enchanted stuff.
So that's a nice thing about D&D's lack of focus--you walk into a room and you never know whether you're going to get Warhammer or Ars Magica. And is the wine on a pressure plate that puts a spike through your eye or is it a gift from the fairies or does it make you grow too big to fit through the door or does it just make you drunk?
In a horror game, the 3 pedestal room would be ominous, because being in a horror game makes everything ominous. But knowing you're in D&D has a subtler effect--it is, simply, disturbing. It's just not quite right. But it might be something. Maybe. Hmmm... Maybe we should... mmmm, I don't know...
The Tree Megadungeon and the Mythic Upperworld
25 minutes ago