I have been doing a bit of thinking and it turns out it looks like this. It's an overview of the setting which I have sent to people contributing art.
The default setting begins in an analogue of New Guinea in the 17th Century, called Paradijs Kolonie (it’s part of the Dutch empire). The crocodile lives in a large lake by a remote village deep in the jungle. It has lived there for centuries, possibly millennia – certainly as long as the village itself has been there. But the crocodile itself is very ancient: it is a relic from the primordial coal swamps from the time before the dinosaurs.
Long ago a shamaness at the village discovered a way to enter the crocodile’s memories. This involved rituals and magic which she kept carefully secret and only taught to one adopted daughter who she selected as the next shamaness. This began a tradition: each shamaness adopts a daughter and teaches her the secret of entering the crocodile’s mind.
The crocodile’s memories, and memories of dreams, form a vast infinite universe which comprise not how the world actually was, but how the crocodile remembers it. In other words, it is the world as it was, but filtered through the crocodile’s suppositions, perspectives, and imaginings. Like all memories, much of it is only tangentially related to reality, and some of it is completely false. It is also attenuated and warped by time and distance and decay. Moreover, it is mixed in with the crocodile’s memories of its own dreams from earlier days. This creates a world that follows unusual anti-logical patterns and reflects not reality but a reflection of it as refracted through a complicated and asymmetric lens.
There are seven different “realms” in the crocodile’s memory, each of which forms chapters in the book. Some are represented as “dungeons”, others hex-maps, and others collections of tables like mini Yoon-Suins.
The Realms of Memory are as follows:
1. Dreams Beneath the Ice. These are the memories of the dreams which the crocodile had while asleep hibernating beneath a vast glacier during an ice age. It consists of a labyrinth of burrows in ice inhabited by the crocodile’s nightmares.
2. Memories of Ruin. These are the memories of the aftermath of the event which caused the extinction of the non-avian dinosaurs. It is a hex map of a huge blasted wilderness, riven by volcanoes and earthquakes. It is inhabited by the crocodile’s memories of dead and undead non-avian dinosaurs, scavengers like turtles and crocodiles, and the birds and mammals which were poised to inherit the new earth.
3. The Dreamtime of Man. These are the crocodile’s memories of early humans. Because the crocodile did not stray far from rivers in those days, its memories are a huge network of rivers all interconnected, with areas of land in between which are infinitely wide. It is inhabited by the crocodile’s memories of early humans and the megafauna which existed at the time.
4. The Infinite City on the Water. This is the crocodile’s memory of an ancient Venice-like city of canals and docks which it observed from a distance while journeying across the oceans. The colourful clothes of the human population seemed to it like birds, so it remembers the city as being populated by strange bird-men. It is infinite, because the crocodile never entered it and thus never saw the other side.
5. The Trade Winds. This is the crocodile’s memory of the vast archipelagos of the South Pacific, which it swam around in eons past. It witnessed the colonisation of these islands by human peoples, and imagined their boats as strange ocean-dwelling beasts: that is what it now remembers.
6. The Underwater Ziggurats. This is the crocodile’s memory of Atlantis-style cities constructed in distant millennia which are now ruined and submerged in shallow coastal waters. They may or may not have been constructed by aliens (this is the least developed of my ideas; I have never been a fan of the “Aliens taught the Ancient Egyptians/Andeans/Minoans how to build!!!!1” theories espoused by eccentric conspiracists, so I wouldn’t want people to think that was what I was alluding to, but I recognise it could be cool for gaming purposes).
7. The Primordial Swamp. The primitive, early coal swamps of the young Earth, into which the crocodile was born, populated by the memories of strange amphibian and reptilian creatures which lived in that cradle of vertebrate life. Also contains many varieties of crocodilian – including the memories of the parents and siblings of The Crocodile itself…
That is the basic geography of the megadungeon. I think of it as the first layer of the setting. There is a second layer on top, which fundamentally changes the contents and aesthetic of the first layer.
The second layer is the Seven Who Went Before. These are seven heroes, wanderers or adventurers who entered the crocodile’s mind in ages past for various reasons, and stayed there. Each of them, naturally enough, has made home in one of the “realms” of memory, and caused changes in its contents. This is for two reasons:
Reason a. If somebody enters the crocodile’s mind and interacts with the memories there, he or she creates new memories which the crocodile now falsely “remembers”. So if you were to enter the crocodile’s memory and, say, teach a creature there how to use a sword, the crocodile would now remember those creatures being able to use swords. It would also remember you – although in the not-quite-right way that all memories are.
Reason b. If somebody with significant puissance enters the crocodile’s mind and stays there, his or her memories and memories of dreams may start to exert an influence there and manifest themselves as “real”. This is because, the longer one stays in the crocodile’s mind, the more one becomes a part of it, subsuming one’s consciousness into that of the great reptile, but also altering it with the contents of one’s own mind.
So each of the Seven Who Went Before has fundamentally altered the character of the “realm” in which he or she is in. While parts of it are “pure” memories of the crocodile, other parts are amalgams of its memories and those of whichever of the Seven is nearby. This manifests itself as follows.
1. The Dreams Beneath the Ice are inhabited by Sese-Mahuru-Bau, a young jungle warrior/hunter who entered the crocodile’s mind in search of a dowry to pay the father of the girl he loved. Because of his presence in the Dreams, there exist beings from the legendarium of his tribe there too, as well as his memories of his forest home. Also, because he brought with him a very puissant sense of love, passion, lust and competitiveness, that has affected the entire character of everything around him.
2. The Memories of Ruin are inhabited by Abu Yaqub al-Sijistani, a Neoplatonist philosopher from the Near East circa 900 AD. He entered the crocodile’s mind in search of truth and enlightenment – of oneness with the universe. Because of his presence in the Memories, there exist many philosophers, religionists and supernatural beings from his memories and dreams there now too, as well as the keen sense of the power of philosophy and the mind amidst the inhabitants.
3. The Dreamtime of Man is inhabited by Pape Jan, or Prester John, a medieval Ethiopian Christian king who entered the crocodile’s mind in order to convert its inhabitants to Christianity – by fire and sword if necessary. Because of his presence in the Dreamtime, the primitive inhabitants are swept with religious and missionary urges, and fight religious wars as ferocious as any such struggle in the “real world”.
4. The Infinite City on the Water are inhabited by Jorge de Menezez, a Portingale conquistador who came to the village in the jungle and, on hearing about the crocodile, decided to conquer its memory world and bring its contents back to Europe for his King and the Pope. He is a bloodthirsty killer who took into the Infinite City steel armour, swords, and black-powder weapons, and those things have become part of the memories of the crocodile now. Moreover, Jorge de Menezez’s violent nature has also exerted its influence. This makes the Infinite City a place perpetually at war, divided between arquebus-wielding factions of colourful man birds, all of whom fight eternally over its treasures.
5. The Trade Winds are inhabited by Xu Fu, a Chinese wizard from ancient days who came to the village in the jungle in search of the mythical Mount Penglai, the land where the Eight Immortals live, and whose fruit provides eternal life. He entered the mind of the crocodile thinking it may be there. It was not, but the power of his vision has created something like it in the crocodile’s memory: a mountain-island in the middle of the great ocean – a weird Shangri-la which the men from the sea are endlessly seeking in the journeying.
6. The Underwater Ziggurats are inhabited by Anak Wungsu, a Hindu trader from Bali who entered the mind of the crocodile in order to try to find things there to bring back for sale. His obsession with commerce has altered the memories of the crocodile, such that the alien inhabitants of the underwater ruins now create vast and complex trade networks, as frequently riven by trade war and colonialism as the South China Sea in the middle ages.
7. The Primordial Swamp is inhabited by Ebu Gogo. She is the matriarch of an obscure branch of hominid from the Spice Islands, rendered extinct by genocide and disease in an invasion by Portingale privateers. She fled and ultimately found her way to the jungle village, and entered the crocodile’s mind to start a new tribe. She breeds with the strange lifeforms of the ancient times, and the crocodile now remembers its distant birthplace that way – inhabited not just by early amphibians and reptiles, but by the hybrid progeny of those creatures and bipedal hominids.
So that’s the second layer of the setting. There is then a third layer, which is what effect the PCs have on the crocodile’s memory when they enter. I’m currently thinking that through.