Widdershins is to four-dimensional dungeons what Arrakis was to breach dungeons, and what Nightmare is to psychic dungeons.

Most four-dimensional dungeons are not actually all that four-dimensional.  Even Escher was mostly a regular fiendishly complicated gravitationally-inconsistent labyrinth, with only a few inches of four-dimensional clearance ana and kata of its main layout.  The space that Widdershins occupies is a perfect tesseract: a half-mile long north-south, east-west, up-down, and ana-kata.

Up-down is a bit of a misnomer.  In Widdershins, down is kata.  That is, the three-dimensional hyperplane into which you emerge when you step through the Widdershins entry portal is perpendicular to the direction of gravity.  The moment you emerge from the portal, you begin falling in a direction you cannot perceive.  What this looks like to you is being suspended in midair while blobby shapes reminiscent of fiberglass horses change shape spasmodically and violently in no pattern that you are able to track, until they

stop.

Quite suddenly.

(They look like they might be hooves, now.)

You're on the ground, but you wouldn't know it to look in any direction you can find.  To all appearances you are still suspended in midair.  A moment ago you felt a sharp thud throughout your entire body.  Now, any muscular action of any kind anywhere in your body, voluntary or otherwise, will give you an intimate and personal appreciation of what it feels like for a bird's feathers to be pet in the wrong direction.  You have landed flat on the ground, as flat on the ground as a human being is capable of being: every part of your three-dimensional surface, inside and outside, is flush with the three-dimensional surface of the flat ground of Widdershins.

Try to stand up!  You can't.  You have no muscle fibers that can contract to pull any part of your body perpendicular to the three dimensional space you occupy.  You will need telekinesis, your own or somebody else's, and you will need telekinesis that is capable of rotating you through the fourth dimension.  Can anyone on Earth do this?  Is there anyone on Earth with both a framework for telekinetic powers that allow them to work in an extra dimension, and the expertise to understand how to do it?

In a word, no.

You need three experts.  You need a very good telekinetic; you need a 4D sensor; and, realistically, you need a psychic - someone capable of transmitting thoughts back and forth between them.

The best 4D sensor in the world is a cat, and he thinks you are being awfully dramatic about all of this.  The second best 4D sensor in the world is a man named Sightline.  He has helpfully filled the air surrounding you with floating four-dimensional eyeballs.  (Eyehyperballs.)  They blink in and out of existence as frequently and suddenly as your own meager 3D eyes dart back and forth between their lids.  (Remember also that every cubic centimeter of your eyeball is sliding along the three-dimensional ground every time it moves.)  The best all-purpose telekinetic in the world is Athena.  Is Athena here?  Maybe this is what she was doing during Arrakis's attack on Toronto.  The best voluntary telepath in the world doesn't have any fucking clue what he's transmitting but by god he is going to transmit it if it kills him.

You levitate upwards - anawards - off the ground - and begin to rotate.

At first this looks like the reverse of what you experienced four-and-change paragraphs ago, and then it gets worse.  Shapes stretch and skew and smear, balloon and shrink and wink out.  The ground appears, infinitely distant at first and then rushing toward you at terrifying speed - but slowing, solicitously, as it approaches, until you are floating a few feet above it.

You are gently set down.

Congratulations, seasoned dungeoneer!  You have stood up.

You are no longer wearing clothes.

In fact you are no longer wearing or holding any armor or equipment of any kind that you may have brought into the dungeon.  The reason for this is simple.  Picture a jigsaw puzzle.  Now picture trying to stand it up vertically.  That is what happens to you when you try to stand up in the fourth dimension.

Widdershins will magnanimously allow your entire body to remain co-hyperplanar with itself, a single perfectly flat three-dimensional puzzle piece.  It will magnanimously allow you to balance perfectly on your edge, and even walk back and forth in the directions you're accustomed to walking in.  But it will not extend this geometrical grace to anything outside of your body, any more than a water dungeon which prevents you from drowning will stop your gun from getting wet.

By the way, when you imagined that jigsaw puzzle collapsing as it stood on its edge, and all of its pieces landing in a heap, did you imagine those pieces landing standing-up on their edges?  No, you didn't.  Anything that fell off of you when you stood up is also cross-sectionally flat along the ground, and if you're very lucky you're seeing a wafer-thin cross-section of it next to you.  If you try to pick it up, it will tip right out of your hand - that is, it will blibble rapidly into a differently-shaped cross-section and then disappear.

So any equipment you want to bring into the dungeon will also require the personal attention of one of the world's several best telekinetics, and one of the world's several best 4D sensors, and one of the world's several best telepaths.  And if it has any internal components, then one of those people better understand in intimate detail how those components should be held relative to each other, lest they just flop out the bare sides.  And if it has any sensitive internal components, that shouldn't be exposed to the air, then lol, lmao.

Anyway, that about covers your first fifteen seconds inside Widdershins.  Are you ready to begin exploring?