Tales of mythical beasts once believed to inhabit East Yorkshire and Lincolnshire have inspired themed sculptures.
The creatures form the basis of a spooky walking trail at Tophill Low Nature Reserve near Driffield.
Geologist Richard Myerscough said early fenland settlers would invent stories to keep their children safe from venturing out into the marsh.
“They would hear peculiar noises in the night, not knowing what they were,” he said. “Out in the bogs methane would ignite forming Willow the Wisp fires and again, they would see those at night.”