This is a really tough one. The fantasy universe is full of oddities of various types and sources. In creatures we have strange beings such as the were-mole and aboleth. In magic items we have things like the belt of gender change. The list of odd planar locations seems to have no end. But there is one oddity that has endlessly fascinated me since I first came across it: The World Serpent Inn.
About the Inn
There is a TV trope referred to as the “Inn Between Worlds“. This is a place that wanders from place to place. A building that appears and disappears, seemingly at random. It serves as a portal between worlds and in one variety or another is often used as a means of crossing over between realities. The World Serpent Inn is the D&D equivalent of it.
It’s been around since the days of AD&D and received a big treatise in Dragon Magazine #351 (which I still have around somewhere). The Inn can be used by travelers to easily get from Krynn to Greyhawk to Faerun or to just about any plane that exists in the D&D cosmology.
There’s a large common room that changes from time to time. Numerous passageways filled with doors. Some of the doors lead to rooms and some of them lead to various otherworldly destinations and times. The passageways and doors are not fixed constants, either. They seem to change at random, appearing and disappearing and changing where they lead.
The Dragon magazine article detailed a number of cool side quests and adventure hooks that could be undertaken from the Inn. One example was a door that leads to Istar just days before the gods of Krynn blasted it into oblivion.
The Inn is something that I’ve co-opted for my own purposes within the Wyrmfang Chronicles. In my usage, the Inn has a new co-owner, Aeduin (my cleric of the Smoking Eye from the Shackled City adventure path). He has given it a permanent home on the plane that he now controls, Occipitus. Much remains the same, but there are a few notable differences.
The bartenders who work behind the bar are three medusae, sisters that he rescued from somewhere. Neither he nor they talk about the where or how of it. New patrons may wary at first, but the sisters never turn anyone to stone unless they are causing problems. They are, in effect, the bouncers.
Another change is that there are many more hallways and doors than there were previously. Aeduin has turned the Inn and the plane of Occipitus it now resides in, into a place of neutrality where friends and enemies may come to negotiate, discuss, or just drink together. Fighting is strictly prohibited. One may see elves from Silvanesti seated around a table with those from Evereska. Or mind flayers and githyanki negotiating over some piece of the Ethereal. Even the occasional avatar or demi-god may drop by for a drink or two.