D10 Strange Worlds and The Portals That Transport You

Have you ever wanted to throw your players into a horrible world of woe and despair for a few sessions?  A fun distraction on the side to the main adventure.  Well, fret no more.  Here are a few seed ideas of worlds your party could be transported to and the method in which they could be taken!

Strange Worlds at End of Eerie Portals
The Portal	The World
1 The surface of a mirror	The Grey Maze: Walls of a grand maze surround you. They reach high into the sky and their uniformly flat surfaces make scaling them impossible. Even the grandest of giants would find scaling such a climb impossible. The repetition of the landscape and the complexity of the maze makes it hard to navigate. If one does not take the time to carefully map their progress it will be easy to get lost forever. Civilisation can be found here, where the facades of the walls are cracked. People build towns within the cracks in the walls. They are well guarded. Spider things hunt in the maze. They scale the walls with ease and carry bony harpoons to capture their prey.
2 A glowing potion that when drunk causes the drinker to fall into a deep slumber and phase-out of reality	The cylinder: The surface of the world in here is found upon the inside of a seemingly endless cylinder. A person can look up into the sky and see the sprawl of a city above them at the opposite side to where they stand. The sun is a filament of light that runs down the centre of this strange world. Day and night are marked by the luminosity of this ribbon of light.
3 A strange sticky fog rolls over the land here. As soon as one enters this area the sounds of animals cease. If they keep pressing forward they will eventually reach the other world.	The Pit: The world is shaped like a vast bowl with all points sloping inwards. At the centre of the world is a vast, and perfectly round chasm. New land is spawned at the edges of this world. Then over the course of decades, it creeps and slides, and tumbles into the pit. The soil is loose here and thus settled civilisations are rare. Nearly everything is nomadic, metallurgy and other heavy industry that requires fixed infrastructure are non-existent. This is the world of the horse lord.
4 A small knife with a uniquely sharp edge is able to cut a hole between worlds. Wounds inflicted with this knife bleed the stuff strange realities.	The Abandoned City: There is a vast city. With infinite floors and infinite sprawl. The echoes of your voice is swallowed by the absurd vastness of this space. You are not sure where the city ends and the sky beings. It is entirely devoid of its previous inhabitants. However strange mockeries of humanity can be found squatting in the rooms of this metropolis. They do not enjoy company. Small redoubts of post-human survivors live. They are a hardy sort who are expert scavengers and cultivators.
5 A great titan of a beast stalks the land. It is said that its throat is a portal to another world. All you have to do is risk being swallowed whole.	Volcanism in The Nightland: The Sun is dying and has all but dimmed to shine out a sickly green glow. The world is either pitch black or illuminated by a weak emerald light. It is a hot and humid place and it is beset by violent and endless volcanism. Volcanoes erupt regularly, vomiting out all but unseen ash clouds, earthquakes are common here. This place is home to a rich and ferocious ecosystem. The hydrothermal vents provide the basis of life here. Great worms feed on the minerals and nutrients exuded. Predators many times the size of a person skitter in the dark, and greater things predate on them still. For such a hostile place civilisation thrives. Though it is penned in and terrified of what lies beyond its borders.
6 A single silver key. Absurdly plain in design. Anyone who holds it may unlock any door which will now open into another world. Be careful. Not every world will have a door to return you.	Ropes and Knots: There is no apparent ground to this world, just an endless sky that falls into a black void. This world is comprised of huge strands of rope that can be anything from a few meters to a few kilometres thick. They go in all directions and meet together in great knots. The knots themselves can vary in size hugely. It is in the larger knots that civilisation is found. Towns and kingdoms claim knots as their home. And within the strands and between the gaps of the ropes are the strange caves and dungeons of this world. The cut one of the great ropes is the greatest taboo of all, for connection is life. Beware the fleet centipede things that hunt in the wild of the strands.
7 A spell or ritual. It is written in a hidden tome or scroll. It is clearly hidden knowledge, maybe to keep the treasure to themselves or to keep our world from danger.	Grass Ocean: This is a world is islands and archipelagoes. These islands are rich oases and plenty and peace, however, they are separated by the grass ocean. Where there would be an ocean there is a great plain of long grass, and like the ocean, the level of the grass is uniform at the surface. The deep one goes into the grass ocean the longer the grass becomes. Travelling from one island is dangerous. Navigating the depths of the ocean is incredibly difficult and dangerous. The deeper you go the darker it becomes due to the fronds of grass blocking out more and more light. Numerous shark-like predators that crawl and creep hunt down here. Though it is also rich in life to be harvested.
8 A portal. A standard glowing portal. You can choose the colour it glows.	The Million Million Rooms: This place could possibly be hell. The world is a series of interconnecting rooms. Some as small as a closet others the size of a cathedral's interior. The walls of this place are the same charcoal colour. The sameness is endless. It's maddening. It hurts one's mind to dwell here for more than a few hours. One cannot tell where a corner or dark spaces begin. There is no food or sustenance here so it is almost devoid of life. Almost. For solid human-like shadows walk these halls. They have the same charcoal colour and they hunt and hate life.
9 A great eternal fire burns at this place. For some, it is a place of pilgrimage. Some sacrifice themselves to the flame. For those that do they are transported to another world.	The Tireless Strider: The world is a vast clockwork golem. It is the size of a continent that it marches ceaselessly through an endless mist that obscures anything below its waste. Upon its back shoulders and head, cities have grown. They are prosperous and thick with culture. Adventures will often delve into the golem itself. Within are items of great use and power. But within are guardians of the golem's body, as well as other things that stalk in the dark. The question begs. Where is the golem heading to, and will it ever reach its destination?
10 A lake with a perfectly flat surface that never ripples. Once submerged and drowning you will awake in another world.	Puppets and Palaces: The world is normal. It has kingdoms, economies, peoples and passions. Except everyone one is a puppet. They will deny it of course, even if you show them the strings that hold them up. Are they actually individuals? Or is some strange eldritch creature playing dollhouse with a world?