You are in the forested marshlands of Russia, 267 million years ago.

The air in the Permian basin was thick, humid, and smelled intensely of sulfur and rotting vegetation. You sat completely still, partially hidden by a thicket of towering calamites, observing a muddy, slow-moving riverbank.

A herd of Estemmenosuchus had taken over the bank. They looked like nature’s ugliest, yet most magnificent, experiment. They were massive—easily 15 feet long—with mottled, glandular skin that looked slightly damp, much like a hippopotamus or a hairless mammal.

The real shock was their heads. The males were adorned with elaborate, branching antler-like horns, giving them a "crowned" appearance. Two large males were challenging each other, not with speed, but with sheer, stubborn presence. They pushed against each other, their sprawling, bulky bodies heavily straining in the mud. They wasn't screaming, but emitting low, guttural grunts.

They weren't the fast-paced monsters of the later dinosaur era; they were slow, heavy, "crowned crocodiles" of a stranger time. One of them, a smaller male, turned its massive skull towards you, its eyes dull and indifferent. You didn't move. They were walking nightmares, a mix of reptile and mammal, and they were the masters of this humid, forgotten world.