You are in the coal forests of Scotland, 300 million years ago.

The air in the swamp was thick, hot, and smelled intensely of sulfur and rotting vegetation. You were pushing through massive horsetail reeds when a sound like a small helicopter forced you to freeze.

It wasn’t a helicopter, of course, since you are in the Carboniferous period.

A streak of translucent emerald and black zipped between the colossal ferns. It landed on a mossy log just five feet from you, its wings clicking shut like locking windows. It was a Meganeura. Even knowing they existed, you weren’t prepared for the scale—its wingspan easily stretched over two feet, and its body was the size of a pigeon.

Its head was almost entirely made of two massive, multi-faceted eyes, swiveling in place like headlamps, instantly focusing on you. You held your breath, terrified to move. Spines lined its long, dangling legs, designed for catching smaller prey, but those enormous, sharp mandibles looked like they could handle something much larger. It hovered again, shifting in mid-air with impossible agility.