The Age of Giants

The world after the Triassic extinction

The Jurassic does not begin with the first giant animal, or even with the first giant dinosaur. Its importance lies in what happens after the end-Triassic extinction: dinosaurs survive a planetary crisis that removes many of their competitors, then spread through the ecological space left behind.

Long-necked herbivores become larger and more numerous. Predatory theropods diversify beside them. Armoured dinosaurs defend the forest floor. Pterosaurs remain the great visible vertebrates of the air, while ichthyosaurs, plesiosaurs, pliosaurs and marine crocodyliforms fill Jurassic seas with predators every bit as formidable as those on land.

The planet itself is changing beneath them. Pangaea continues to break apart. Rift systems widen, the Atlantic begins to open, Laurasia and Gondwana grow more distinct, and multiplying coastlines, islands, wetlands and shallow seas divide populations that once shared broad continental ranges.

Hidden Powers of the Jurassic

Dinosaurs dominate the visible Earth. They do not possess the whole of it.

The hidden chronology also contains extraterrestrial colonies, wars between elder civilisations, minds able to cross time, serpent sanctuaries beneath the continents and ancient roads into fey realms. None of these events replaces palaeontology. They belong to another layer of the same history.

The miners from Yuggoth return in force

The Mi-Go are not arriving on Earth for the first time. They have visited the planet before. Around 160 million years ago, however, those earlier contacts become something much larger.

Prospecting stations multiply into mines, laboratories and biological-extraction colonies. Concealed operations spread through remote mountains, cavern systems and northern territories. The Mi-Go seek minerals, living specimens, unusual chemistry and knowledge that can be carried back into their wider network.

Jurassic life interests them as material rather than myth. A sauropod, giant marine reptile or predatory dinosaur can be specimen, hazard, resource or experimental subject. Their expansion might have remained another hidden episode of alien exploitation had Earth not already been occupied by a civilisation old enough to regard much of the planet as its own.

The war with the Elder Things

The Elder Things are not archaeological ghosts during the Jurassic. Their civilisation is still alive, technologically formidable and spread through functioning settlements, marine cities, laboratories and deep installations. Their greatest centres lie increasingly towards the south and within their ancient Antarctic sphere, but their presence extends far beyond it.

Mi-Go expansion eventually collides with territories and resources the Elder Things continue to claim. Raids and local clashes grow into a full-scale extraterrestrial war fought beneath oceans, through mountain complexes and across remote regions that will leave no human historical record.

The Mi-Go gain the advantage across much of the north. Important territories fall to them, while Elder Thing power is pushed back from regions it had occupied for immense spans of time.

After the victory, the Mi-Go retain a persistent but changing terrestrial network of mines, mountain and subterranean bases, laboratories, observation stations, biological-research facilities and deep-Earth routes. Individual installations can be abandoned, destroyed, reopened or replaced across geological time; the network waxes and wanes without becoming an open Mi-Go empire or requiring any one Jurassic base to remain continuously active into 1454.

This is a major defeat, not the destruction of the Elder Things. Their Antarctic centres, southern installations, marine cities and deep complexes survive. In some former territories they leave only abandoned works behind; elsewhere their civilisation remains active and dangerous.

Yaddith-Gho and the land later remembered as Mu

Not every Yuggothian presence belongs to the same colonial system. A related but distinct people remembered as the Spawn of Yuggoth reached Earth before terrestrial life, built Yaddith-Gho in the region later associated with Mu and brought or installed the terrible entity Ghatanothoa. The Spawn later perished aeons before human Mu.

During the c. 160 Ma Mi-Go expansion, explorers recognise Yaddith-Gho as a primordial site of a related Yuggoth civilisation. They investigate its outer ruins, confirm that Ghatanothoa still survives beneath the fortress, and quarantine or avoid the site rather than reoccupying or exploiting it.

Yaddith-Gho therefore remains a dead primordial fortress through the Jurassic, bound to Ghatanothoa and awaiting the vastly later human civilisation remembered as Mu.

The name survives more reliably than Jurassic geography. Continents move, coastlines vanish and seas open or close across tens of millions of years. SpiralWorlds preserves the later tradition of Mu without projecting a human-era map unchanged into the Jurassic.

War through mind and time

The Yekubian threat begins not with an army but with a single cube.

The beings associated with it possess a more insidious method of invasion: the exchange of minds between bodies. Yekubian minds begin occupying terrestrial hosts, offering a way to establish themselves without armies, fleets or a conventional landing.

The Great Race of Yith recognises the danger and responds without hesitation. Rather than allow the exchange to become a stable bridgehead, the Great Race destroys the bodies occupied by the intruding minds and prevents the Yekubians from consolidating their presence.

The original cube is captured, studied and quarantined. Later Yekubian cubes fail to reach Earth.

The Eltdown Shards

Knowledge of the encounter survives within the records of the Great Race. The writings later known as the Eltdown Shards are connected to that history, but they are not ordinary Jurassic tablets left in a place conveniently corresponding to later England.

They are temporally displaced Great Race records. Their appearance in later geological contexts is therefore evidence of beings able to move knowledge across time, not of human geography somehow remaining unchanged for more than a hundred million years.

Survivors beneath the giant roads

The destruction of earlier serpent dynasties does not erase the Serpentfolk. Survivor lineages remain within sealed under-realms, ancient ruins, hidden sanctuaries and concealed enclaves. They do not recover a single worldwide Jurassic surface empire, but neither have they disappeared.

Elder Thing civilisation continues elsewhere despite the losses inflicted by the Mi-Go. Some abandoned installations become ruins beneath younger landscapes, while other settlements remain inhabited.

Deeper still lie regions marked by the much older Shoggoth rebellion. The rebellion itself belongs to an earlier age, but its consequences survive. Shoggoths and descendants of Elder Thing biotechnology remain within depths where the changing surface world has little relevance.

The Shining Trapezohedron is already ancient as well. Fashioned on Yuggoth and in Elder Thing possession long before the Jurassic, it remains associated with their Antarctic sphere during this age. Its later passage into Serpentfolk hands lies further ahead.

Above these buried histories, fey crossings continue their Jurassic resurgence. Old roads reopen between immense forests, wild waters and ancient courts. No single fey power rules the planet; some territories answer to particular courts, others to different traditions, and much of the world remains simply wild.

The giants do not vanish at the boundary

The end of the Jurassic is not a mass-extinction curtain. Dinosaur dynasties continue into the Cretaceous, continental fragmentation continues, and regional ecosystems become increasingly distinct. Feathered theropods keep diversifying along evolutionary paths that will produce the extraordinary radiation of birds.

Dinosaur dynasties

Sauropods, theropods, armoured dinosaurs and many smaller lineages cross the boundary and continue evolving within the changing Cretaceous world.

Bird-line dinosaurs

Feathered theropods carry dinosaurian inheritance into increasingly specialised aerial forms. The emergence of birds does not end dinosaur history; birds are one surviving branch of it.

Mammalian persistence

Mammals remain small beside the dominant reptiles, but continue expanding through niches that reward nocturnal life, climbing, burrowing and dietary flexibility.

Buried inheritances

Mi-Go workings, abandoned Elder Thing installations, surviving deep Elder Thing settlements, serpent sanctuaries, sealed Yuggothian sites and fey-anchored wild places can outlast geological change as functioning enclaves, buried complexes, relics or supernatural territories.

The next age will not replace the dinosaurs. It will transform the world around them. New plant communities, changing relationships with insects, rising seas and increasingly separated continents will create the conditions for the final great dinosaur worlds.

The Jurassic is still beneath the campaign world

More than a hundred million years later, the Age of Giants can return as creature, place, object or claim. A Jurassic adventure does not have to become a tour of prehistoric exhibits. The useful question is what survived—and who wants it now.

Primeval refuges

Hidden valleys, deep caverns, isolated islands and other protected environments can preserve lineages long after they disappear from the ordinary surface world.

Alien extraction sites

A Mi-Go mine buried beneath later mountain-building may contain impossible alloys, biological archives, preserved specimens or machinery never designed for human hands.

Ruins below ruins

A medieval fortress may stand above Roman stone, Bronze Age foundations and Neolithic ritual ground—and beneath all of them an Elder Thing complex, serpent sanctuary or Mi-Go installation millions or billions of years older.

Some of those places are genuinely ruins. Others were merely sealed, abandoned from the surface or left waiting.

Monsters without a human past

A surviving Jurassic animal requires no forgotten wizard, divine curse or ancient legend to explain it. Sometimes its greatest horror is precisely that it is natural: an animal from a vanished ecosystem that has no interest in human history at all.

Explore the World Bestiary →

Scientific reference points

The real chronology remains the foundation. These references support the geological boundaries, Jurassic environments, fossil-record limitations and dinosaur-to-bird material used throughout the page.

Dates in deep time change as stratigraphic calibration improves. Older references may still round the Jurassic–Cretaceous boundary to about 145 million years ago; this page follows the June 2026 ICS value.

The world keeps changing

The dinosaurs leave the Jurassic still dominant. Ahead lies a more fragmented planet, changing plant communities and the final great expansion of dinosaur diversity before the catastrophe at the end of the Cretaceous.