Dungeons and Dragons is a magical game full of magical creatures. There are majestic monsters scattered all throughout the lore of D&D, and those that aren't so majestic. Dungeon Masters looking for tips on how to spice up their games may want to look into some of these weird creatures, as the bizarre ones can be an awesome way to get players more involved in a specific region of a campaign, and perhaps even go hunting for more strange creatures, which is always a fun time.
A chasme is a classic case of a scientist that accidentally crossed their DNA with a fly's, except in this case the fly is a demon. Like any fly, they're capable of landing on ceilings or walls and are often used as interrogators by more powerful demons. What's most unsettling is the chasme's long, pointed nose, which would put even the most aggressive woodpeckers to shame.
14 Intellect Devourer
Picture a brain with massive legs. That's an intellect devourer. The creature feeds on the intelligence of sentient creatures, and can even take over a body for a mind flayer, which acts as the monster's master. The creature is pretty similar to a licker from Resident Evil, though a bit less unsettling thanks to the absence of a real torso. Still, it's not the type of creature anyone would want to snuggle up with.
Another creature that's mostly a brain, a grell is seemingly a half bird, half jellyfish creature. They have no eyes and use a type of levitation to float. However, their skin is sensitive to vibration, and thet have an impeccable sense of hearing. They float silently waiting for the perfect moment to strike lone creatures or a straggler in a group, making it a deadly creature too.
An Aboleth is basically an octopus made of pure hatred. They're a sort of telepathic fish capable of dominating lesser creatures, at one point even holding an entire empire before the gods destroyed it and freed their slaves. Aboleth are pretty ancient creatures, existing in the primordial oceans of the Dungeons and Dragons mythos, and still inhabiting some their ruined cities from the peak of their empire, now lost in the depths of the sea.
Falling pretty sharply in the "humanoid spider" camp, an ettercap is actually a fairly unthreatening looking creature, if you can get past its beady black eyes, claws, and face prongs. It's capable of spinning webs from its abdomen, entrapping and consuming any adventurers foolish enough to wander into its lair.
A stirge is a horrifying cross between a bat and a mosquito. Like a mosquito, a stirge survives off the blood of other living creatures. While it's still a tiny monster by Dungeons and Dragons standards, it would be a massive pest in the real world. Not to mention, they can also travel in packs, each one latching on to a vulnerable part of another monster as they drink their fill. That being said, they only have 2 hit points, which is probably about as much damage as an electric flyswatter does.
Stalagmite? Stalactite? Who cares, when an innocent-looking rock formation may actually turn out to be a flesh-eating monster. A roper will eat anything that wanders too close to it, often attacking quickly and surprising its prey. It has one big, unsettling eye, that snaps open just before it begins devouring its catch. All in all, it looks suspiciously similar to a squid made out of rocks, though the only thing that could make it more unsettling would be the ability to shoot ink as a defense mechanism.
A yochlol looks just about as weird as its name sounds, at least in its true form. The creature is described as "a tower of yellow slime with a single malevolent eye" in the Monster Manual, which is about as accurate of a description as it's possible to get. The monster is also able to take the form of a female drow or a spider to conceal its true form, but its touch is pretty much always venomous.
A behir is twisted monstrosity resembling a centipede and a crocodile. If that in itself isn't the stuff of nightmares, it's also able to shoot lightning breath. Plus, it can clamber up walls, so there's no telling when one is going to leap down on a brave adventurer to turn them into lunch. Behirs were created by Storm Giants to fight dragons, and they certainly look terrifying enough to put up a good fight against one.
Modrons are curious little creatures. Their society values law and order above all else, with a strict hierarchy in place. A modron will only communicate with another modron immediately above or below it in the hierarchy, with no sense of self - except for fulfilling their duties within the society. In a way, it's the perfect fit for their cog-like look, which makes them one of the more unique creatures in the D&D mythos.
The lemure is essentially a shapeless pile of flesh created when a mortal soul is sent to the Nine Hells for all of eternity. While the creature still looks vaguely human, it's mostly due to the rough shape of a torso and agonizing facial expression that it's always doomed to wear. It doesn't help that it's one of the weakest creatures out there, too, making it seem pitiful, above all else.
An Otyguh is that childhood friend that never made anything of themselves. It spends its time buried in a mound of blood, guts, and entrails, waiting for absent-minded prey to walk by. It then surprises the creature with its tentacles, erupting from the meat mound to capture and kill whatever it manages to grab. Not to mention, it has some telepathic abilities and is capable of tricking creatures to come to its lair.
3 Gelatinous Cube
A gelatinous cube is a deadly creature, yes, but it also seems like one that a trapped adventurer could eat their way out of. The cube slowly descends on unsuspecting prey, enveloping and slowly devouring it. It's almost completely transparent, making it difficult to spot in dimly-lit dungeons and other dark areas. Still, it's really just, well, a big blob of mean Jell-O, bent on consuming living tissue - making it weird, but not all that threatening.
2 Gibbering Mouther
If there are any creatures in DnD that are truly the thing of nightmares, it's a gibbering mouther. The creature is a blob of mouths and eyes, that "propels itself by oozing forward". Each mouth cries out in a different tone when it detects prey, causing most creatures to flee. The gibbering mouther is a truly haunting being, leaving behind nothing of the prey it consumes. Except, of course, the mouth, which "boil" to its surface and join the creature's other mouths.
A Flumph looks like a Plumbus from Rick and Morty crossed with some form of starfish and octopus hybrid. Their name comes from the sound they make as they're propelled through the Underdark, making them all the weirder. They're also a lawful good creature, which really just makes them seem cute in a way - though they do pass on the dark secrets they learn to good-hearted adventurers, making them kind of a bummer to be around. However, a group of Flumphs is called a cloister, and "a cloister of Flumphs" is just fun to say.
Of course, these are just a few of the monsters present in the Monster Manual. While they are some of the weirdest, there are still plenty of other bizarre and interesting creatures to consider adding to a campaign - or even just to read about. Really, the Monster Manual is one of the things players will probably need to get started with Dungeons and Dragons, though the amazing art is a cool added bonus.