11 Of The Strangest Monsters In Roman Mythology

If you were to approach a modern-day biologist and ask about the basilisk, you'll likely get a rundown of the tropical lizards that go by that name. And while that may make a herpetologist's heart sing, these lizards — which are admittedly pretty cool, with crests on their heads and the ability to run on top of the water under the right conditions — aren't quite what the Romans had in mind.

For Romans who read Pliny the Elder's "Natural History," the basilisk detailed inside was a frightening monster. He describes it as a serpent that somehow moves upright by locomoting with the middle section of its body. It's frightfully dangerous, in large part because it exudes a vapor so poisonous that anything it touches or even breathes on burns. Pliny notes that it's easy to figure out where the basilisk lives, as it's surrounded by a devastated landscape. Roman poet Lucan makes similar claims in his epic work, the "Pharsalia."

Anyone who attempts to kill the basilisk is pretty much doomed, Pliny writes, as the monster's poison would flow up a weapon and kill the wielder. Sitting high up on a horse wouldn't lend a helpful distance, and the would-be basilisk slayer would end up with a dead horse besides. The only creature believed to be able to defeat the basilisk (albeit in a battle that ensured death all around) was a weasel. The seemingly humble predator isn't just tenacious but was said to emit a miasma that acted as an antidote to the basilisk's mega-poison.

You may think you have the concept of the centaur down. It's a creature with the body of a horse, only with a human upper half sprouting from the front shoulders of the animal. Depending on the artist, a centaur can look majestic or ridiculous, but there really isn't much room to experiment with the form, right?

Sounds like you haven't heard of the onocentaur. The earliest Greek descriptions of this creature sound a lot like our more-or-less modern understanding of the centaur, while slightly later accounts get the creature confused with wild dogs and even frightening demons. But by the time things got to the Romans, this monster got significantly weirder. Aelian — admittedly a Greek writer, but one who wrote in the second century and whose works would have been read by Romans — agreed that the onocentaur had the upper body of a human. But his description then states that the lower part was only the back half of a horse, leaving the onocentaur to totter around on two hooves. 

Not to worry, however, as the creature was said to lean forward onto its soft human hands when it needed to run. Not that you would have been able to ask the onocentaur how such locomotion worked or how it felt to try and get soft human hands to act as feet. That's because the onocentaurs were said to be viciously aggressive and dangerous to humans who crossed their path.

According to folklore, ancient Rome was stalked by many different ghosts. There were the lares, good spirits who didn't cause much trouble. So, too, were the manes, at least further back in Roman history. Later writers got them confused with the ghosts of individual humans or general ancestor figures, while others maintained that the term was a catch-all for spirits who hadn't made their alignment on the good-to-evil scale clear.

Then, there were the lemures. These were ancient Roman spirits who meant business — and their business was none too good. Some said that these frightful spirits were simply evil and existed to torment humans. Others, like the poet Ovid, supposed that the lemures were manes or ancestors gone bad because no one had been properly attending to their memory or they had unfinished business. Other Roman writers only took the opportunity to deride the whole idea of scary ghosts and anyone who believed in them. The idea was powerful enough that the spooky eyes and night calls of the Madagascar-based prosimians we call lemurs inspired the name.

Perhaps the strangest aspect of the lemures had to do with how the Romans attempted to please them during the Lemuria festival. Held on three non-consecutive days in May, this festival saw ancient Romans scrambling to appease family spirits by untying knots, walking barefoot, and tossing black beans about the house. Ovid claimed that this last trick was meant to distract the formless, vengeful lemures away from the living.

Giants are already pretty odd when you think about them. It's not just their stupendous size (though that's definitely part of it). They're also depicted as bloodthirsty subhumans, from the super-sized Cyclops of the ancient Greek "Odyssey" to the main villain of Jack and the Beanstalk. Fueling these sorts of stories in ancient Rome was the archaeologically substantiated presence of real people living with gigantism, a growth disorder that made them much, much taller than average — but almost certainly did not induce any sort of bloodlust.

Rome had its very own homegrown giant who was supposed to have lived on the city's Aventine Hill, though he caused chaos before the settlement that became Rome was established on the site. Some tales said that Cacus was only a human cattle rustler who lived in a cave on the hill. Later accounts transformed him into a fire-breathing giant who faced off against Hercules. He was said to be the son of the forge god, Vulcan. But his divine heritage didn't do much for his personality, as Cacus' abode was decked out with the gruesome remains of animals and any humans who crossed him. 

When Hercules seeks him out for the crime of stealing cattle, Cacus attempts to create a literal smokescreen in some tales or else goes straight to belching flames into the legendary hero's face. Whatever Cacus tried didn't work, however, as Hercules did him in with a club, and the cattle-hungry, flame-spewing giant of Latium was no more.

Cape buffalo (pictured) are already pretty terrifying. Besides the fact that these large African animals are not only real but seriously hefty — mature males can weigh close to 2,000 pounds — they are notoriously ill-tempered. Some of the more dramatic stories of its destructive power are overblown, but they remain a force to be reckoned with. These animals aren't afraid to fight back when cornered, using their tremendous bulk and those wicked-looking horns to do great damage to their enemies.

The fearsome Cape buffalo may have inspired Greek and Roman tales of the more fantastical catoblepas, which was also said to have lived in sub-Saharan Africa. While it reportedly had the body of a buffalo, things started to get strange when you considered other parts of the monster. Pliny the Elder wrote that its head was so heavy the animal walks around with its skull sagging toward the ground. Just as well, given that its gaze was so deadly that anyone who looked the catoblepas in the eyes dropped dead right away. Pliny then blithely moves on to the topic of basilisks, never bothering to explain or guess how a heavy-headed ungulate was able to murder someone with nothing more than a glance.

For the ancient people of the Mediterranean, the sea represented both great bounty and terrifying death. It's no coincidence that some of the earliest settlements in human history popped up near the sea thousands of years ago. Certainly, the Romans had a lot to thank for their proximity to the Mediterranean, which allowed them to develop a powerful navy to support their empire-building ambitions. But, still, the sea was large and could be treacherous no matter how mighty Rome's collection of trading vessels and warships was. Perhaps that's why Romans joined the other Mediterraneans in telling stories of the strange monsters that stalked the waves.

Broadly known as the cetus in Latin, this category of sea monster was already talked about plenty in ancient Greece, where the hero Perseus is said to have saved the princess Andromeda from being gobbled up by one. In his retelling of the myth in "Metamorphoses," Ovid refers to the monster as belua ponti, while Propertius calls it the monstris marinis — though neither does much to describe it. Even Pliny the Elder was a bit reticent here, though he says the Phoenicians worshipped a goddess named Ceto, who may have been a striking half-fish deity.

At least the first-century poet Valerius Flaccus comes through with a decent description of the Trojan cetus killed by Hercules. His version of the monster is almost too large to describe, with three rows of sharp teeth, a coiling body, and an eerie gray membrane over its eyes.