Holistic World Building: Lost World Diversification

Lost World zones, in the mode of Sir Arthur Conan Doyle’s “The Lost World” and/or Jules Verne’s “A Journey to the Centre of the Earth”, have become a staple of the tabletop RPG world. Whether it’s fantasy or science fiction, the draw of prehistoric settings and creatures has remained high for years. But the drawback is that a lot of them feel same-y. The same grab bag of fan favourite dinosaurs, the same cavemen, maybe some lizardfolk for spice, and the inevitable jungle and swamp terrain combo. So this post is all about diversifying your Lost Worlds in your world building, to bring a bit of extra fun to it all! 

Defining The Lost World

Traditionally, a Lost World is an isolated location, cut off geospatially and climatically from the larger world. This doesn’t have to be the case though, especially in fantasy world builds. Remember that your world doesn’t necessarily have to hew to real world timelines, scales, or anything else. So you can have these places as just a natural location if so desired. Another way to access them is via time portals, with or without potential long term changes to the world. So whatever method you choose to fit them in is going to work, provided you have some level of world building consistency. 

So once you’ve decided how your Lost World(s) are accessible, it’s time to think about what kind of Lost World you want to have going on. And here’s where the fun is, because there’s a lot of options, many of which only need mild conversion work from what is usually readily made or available. As a bonus, I’ll be drawing on the material produced by PBS Eons to help illustrate some types of Lost Worlds you can make, with links to the relevant videos with each entry. I’m approaching it from a fantasy standpoint, so there’s some YMMV to factor in if you’re using more modern or science fiction settings. 

Examples of Alternate Lost World Designs

Fungal Hell

This is an exceedingly rare choice, and by far the most bizarre and alien to us. This is a Lost world where fungus is the dominant lifeform. Giant mushrooms and other fungus reach to the skies above, as primitive plants struggle around them. The air is heavy with spores and the scent of decay, and the dangers here can be as deadly as they can be innocuous. 

  • Sapient Life: Mushroomfolk, like Myconids. 
  • Monsters: Slimes, jellies, oozes, funguses, and similar “simple” lifeforms.
  • Terrain: Anything that isn’t Arctic or Desert, but it’s going to be humid. 

When Giant Fungi Ruled

Amphibian and Insect Nightmares

In a turn away from dinosaurs, this Lost World features amphibious and insect lifeforms, like the giant temnospondyls and equally giant insects of the distant past. The plant life is more familiar to us, and likely the players too (although the plants are still going to be primitive). Everything here is ever so slightly off, unfamiliar enough to be unsettling, but familiar enough to trick the unwary into letting down their guard. Now, I’ve clumped 

  • Sapient Life: Frogfolk or Newtfolk, Insect peoples too!
  • Monsters: Giant amphibians of all kinds, giant insects, fish, and some slimes, jellies, or oozes. 
  • Terrain: Warm to temperate climates. The main restriction this Lost World has is that its lifeforms need warm climates, and in the case of the amphibians, water supplies. Working around this, it can be extremely effective.

When Giant Amphibians Reigned

The Biggest Frog that Ever Lived 

The Age of Giant Insects

Galloping Crocodillians

Crocodiles and their ilk are objectively terrifying, in the real world and in tabletop gaming. Dip into where the prehistoric evolutionary lines went, and you get creatures that once competed with dinosaurs for supremacy. We’re talking hoofed, galloping crocodilians. Others filled the same role as modern cheetahs. And as a cool bonus? This Lost World can be easily be wandered into without any warning and can span into aquatic settings too!

  • Sapient Life: Lizardfolk and Croc/Gatorfolk. 
  • Monsters: crocodiles; this is where you may need to do some re-skinning and mods on existing monsters to make them. Consider raising their AC or equivalent, improving their bite attacks, and so on. 
  • Terrain: Any warm to temperate, water needs to be a thing in some cases, but not nearly as much as the amphibians. This is a great surprise in a desert biome too! 

The Croc That Ran on Hooves

When Crocs Thrived in the Seas

Arctic Dinosaurs

I’ve been knocking dinosaurs a bit, but there’s a place for them in this too! And that place is the Arctic. Or any other cold climate. Normally these places are associated with Ice Age mammals, but why not have some fun and drop dinosaurs into the mix? In addition to the change of pace, it also opens up a lot of roleplay and world development windows. For example, giants are often associated with these climes, so what if they’re dinosaur herders? Or, given the generally more carnivorous diets of peoples in these climates, they make for great mounts and companions.

  • Sapient Life: Dinosaurfolk with cold weather adaptations, Giants, other cold weather peoples. 
  • Monsters: Dinosaurs! With cold weather adaptations and probably too many teeth for adventurers to be comfortable about.
  • Terrain: Arctic, Antarctic, or any sufficiently cold weather region. 

When Dinosaurs Chilled in the Arctic

Ice Age Times

This is a Lost World that gets slept on a lot because it’s often, for some reason, just the default of many fantasy worlds. You go into the north, there’s mammoths. Plains? Some kind of sabertoothed something. But if you concentrate it, it can can be a highly viable Lost world setting in of itself, albeit one that does usually need some major geographic features to contain its awesomeness from predating the more “advanced” world.

  • Sapient Life: Any, although mammalian and avian types are likely most common. This is where beastfolk tend to shine. 
  • Monsters: Axe Beaks/Terror Birds, Rocs, Mammoths, Giant [insert mammal here], and all that good stuff. 
  • Terrain: Any. There’s no real limits here, so you can fit it in with the appropriate animal/monster life in mor eor less any climate.

The Rise and Fall of the Bone-Crushing Dogs

The Time Terror Birds Invaded

The Giant Bird That Got Lost in Time

The Hellacious Lives of the “Hell Pigs”

Life, Sex & Death Among the Dire Wolves

Adorable Nonsense

Not all Lost Worlds have to be perilous nightmares of things waiting to eat the players. This last Lost World Idea is a fun one, and one that’s generally going to be found on islands, where small things get big and big things get small! This is definitely a “lower risk” setting, but one that’s full of fun and/or silly potential. And that’s your bag, this is definitely the Lost World for you!

  • Sapient Life: Any. 
  • Monsters: Mini and Giant versions of Giant and Mini things, go nuts with it.
  • Terrain: Island, any climate. 

The Island of Huge Hamsters and Giant Owls

The Island of the Last Surviving Mammoths

A Note on Civilizations in Lost Worlds

There’s some uncomfortable colonialist baggage around Lost Worlds, especially in terms of the civilizations that are found in them. They range from relatively innocent imaginings of prehistoric life in the neolithic to outrageously stereotyped racist caricatures right out of the “Colonial Justifications 101: How to Other the Locals” handbook’s super racist margin annotations. This does not have to be the case. The biological life in a place does not determine the technological or cultural sophistication of the peoples living in it, on in the case of a fantasy setting, their magical skill or prowess. Flex your imagination. If the civilization has a route to the “normal’ world, how do they interact with it? And also remember that rampant xenophobia of the “out world” is not a substitute for a culture, and it’s been done to death. 

Final Thoughts

Lost Worlds are fun, and they can be more fun than they generally are by branching out a bit from the established genre norms that we all grapple with in world building. If a basic dinosaur jungle or swamp, or odd paleolithic mammal encounter is your speed, no worries! But if you’re doing some world building and want to change things up, or even have multiple Lost Worlds happening without them feeling like retreads, then I hope this post helped!


  • That’s some evocative stuff. Added to the Blog Database for future reference.

  • Jonathan Becker

    It’d be interesting to take a cue from the trope of “lost-world-culture-that-has-more-advanced-technology” …albeit (perhaps) technology only slightly better understood by the locals than the adventuresome interlopers. An advanced culture fallen on “hard times” and then rediscovered (i.e. the traditional Atlantis fantasy story) sounds pretty cool, and certainly works with some of the stranger magical items and artifacts of D&D: cubes of force, apparatuses of Kwalish, the Machine of Leuk-O, etc.

    Then again, perhaps the lost world culture has a perfect and complete understanding of just how advanced they are, and simply want nothing to do with the “civilized” outer world. Wakanda forever and all that jazz.
    ; )

    The idea of hostile insect peoples (thri-kreen, aspis, etc.) as an organized relentless menace in such a setting sounds pretty awesome. Of course, they’d be at odds with the giant amphibians who see them as ready-meals (and who are used by the cave-folks as mounts, pets, and guards…no wonder the tribes have such hostility towards each other).