Medieval people have a reputation for being superstitious – and many of the supernatural phenomena found in the pages of medieval chronicles, miracle stories and romances are still alive in modern culture. Think ghosts, werewolves, demons, vampires, fairies and witches. But while (almost all) people today regard these beings as entirely fictional, many medieval people believed in them.

For the 13th-century English priest Layamon, it was elves (alven) who gave King Arthur magical gifts and who, in the form of beautiful women, carried him away to the mythical island of Avalun to heal. However, Layamon was careful to say that this was the belief of “the Britons” (Celtic people), which he was simply recording.

While tales of abduction by fairies were sometimes dismissed as delusions, stories of saints’ miracles and natural marvels were usually accepted as true.

A particularly sensational example was recorded in the Life of St Modwenna (an early Irish princess and abbess), written by the abbot Geoffrey of Burton circa 1120-1150. In his account, two tenants of Burton Abbey stirred up a violent feud between the abbot and Count Roger the Poitevin. The troublemakers died suddenly and were buried in haste, but apparently reappeared at sunset carrying their own coffins, before transforming into terrifying animals.

These revenants (spirits or animated corpses) reportedly brought death to the village – only three people were left alive. When the graves of the runaways were opened, they were found to be bloodstained but intact. A formal apology to the abbey and the saint was followed by ritual dismembering of these corpses and burning of their hearts. This apparently led to the expulsion of an evil spirit and the recovery of the surviving peasants.

Many of the creatures found in bestiaries (medieval encyclopedias of animals both real and mythological) fitted here, such as dragons, unicorns and basilisks.

Dragons and unicorns remain popular fantasy characters today, but basilisks are less well known – although a giant one once proved a fearsome opponent for Harry Potter. Basilisks were said to be so poisonous that their scent, their fiery breath and even their gaze could kill. They were attested not only by bestiaries but by the Roman philosopher and botanist Pliny in his book Natural History (circa AD77). They were found in the province of Cyrene, in modern Libya.