You are a molydeus. I'm sorry I couldn't find a nice black-and-white illustration but hey, here's Tony DiTerlizzi's depiction of you! You are a powerful two-headed demon that exists in a strange place in the regular Abyssal hierarchy. You serve the demon lords directly as both intermediary, messenger, and enforcer of their will (kind of like a demon cop), and it's said that some major demons fear you more than they fear the all-powerful balors (the non-unionized equivalent of balrogs.) You look weird: your main head resembles a silver-eyed wolf but you also have an anaconda protruding out of your neck. Oh, you carry a singularly powerful magical weapon, a vorpal axe, that automatically beheads its target should you roll a crit. Metal. You are a caller in darkness, a repulsive and depraved creature composed of the minds of dozens of victims who died together in terror. You appear to be a large, incorporeal mass of fog within which one can observe the many distorted faces of said victims screaming in fear. You have the ability to steal the souls of dead and sleeping people, adding another wailing face to your collection. Animals flee and plants wither in your unnatural presence, and your only purpose in existence is to draw others into your fear-wracked, hellish existence. Also, you never apologize about transphobic comments made in the past, causing some of your previous allies to shun you and have a +2 bonus to saving throws against your mind-affecting powers. You are a displacer beast. Another classic monster straight from Gygax's sick brains! You appear as a sleek blue-black panther with six legs and a pair of long tentacles sprouting from your shoulders. You possess an innate magic ability to bend light around you, making you appear to be a foot or two from your actual position. A pretty useful ability for a predator, if you ask me! Anyone attacking you becomes disoriented, struggling to determine where you actually are while you strike back with your funny-looking tentacles (I don't know why a large cat would use some rubbery tentacles instead of their powerful claws and teeth but hey, every single D&D edition has had them neglecting to use their natural weapons for some reason.) Even though you look like a ****ed-up cat, you can actually speak the Common Tongue and, in some cases, your sharp tongue can be just as dangerous a weapon.
You are a quadrone. You are one of the modrons, an immortal race of outsiders known for their zealous adherence to law, order, and special victim units. You are cube-shaped and winged and kind of steampunk, like everything Planescape. You hail from Mechanus, a plane of existence filled with an infinite number of continent-sized interlocking cogs. You are apparently capable of performing four simultaneous tasks at a time because modrons like their society to be neatly organized: you probably poop four times a day as well. You are a being of pure logic and mathematics and cannot be persuaded to disobey your instructions or betray your cosmic purpose in any way, although from time to time a fatal chaotic flaw (like, say, philosophy) claims one of your kind and turns them into a rogue. As modron society is so rigidly structured, every time one of you dies a tridrone (usually a Spaniard) is promoted to try to take your place, often in vain.
Ah, @Ramza would have been my modron overlord had I carried over my marvelous modron self from 2019. Somehow, I think the dice want me to be something else this year.
You are a cloud giant. I'll admit I had never seen this illo before, having joined the hobby soon after TSR decided to actually have an art budget and stop exploiting high-schoolers, but I will never be able to picture cloud giants any other way anymore: his face says "I'll mess you up", his hips say "are you ready for a good time?" So anyway! You are a member of a race of giants that prefer living (you will never guess where) in floating castles among the clouds. You are nearly 18 feet tall, with silvery-white hair and bright blue eyes, talk calmly, and carry a big stick. You often keep dire lions as pets or guardians, because AD&D monsters tended toward the metal side of the Metal-Twee Fantasy Spectrum. Fourth Edition actually gave you a lot of interesting lore, making you a descendant of Titans that fought the Gods during the Dawn War, and I personally like that approach quite a bit. No word over whether you say "fee-fi-fo-fum" in any edition, though!
Just because I said I already was a monster didn't mean I didn't want a monster like everyone else why do you hate me
You are a rakshasa. Like oh-so-many other AD&D monsters you have a mythological origin, but for some reason Gary Gygax decided to start your entry in the Monster Manual with "Known first in India..." Well, I think we can adventure the reason. You are an evil spirit encased in flesh, a smart and powerful being of magic, with your only objectives being tormenting humanity and smoking from that stylish pipe. People are not sure where you originate; some say you are the embodiment of nightmares, others say you are descended from the crafty daemons that populate Hades, others that you are your own kind of fiends who don't need no origin history. Who knows and who cares. Nowadays you are most commonly depicted as regal-looking humanoid tigers sporting hands whose palms curve backward, away from the body, but Gygax insisted rakshasas could look however they pleased ("some of them look like multiheaded apes", he's known to have said.) Back during the good old AD&D times, you were immune to most spells and magical effects, being a very effective monster to drop on one of those all-powerful magic-users that tended to dominate adventuring groups. Sucks to be them.
Many people are saying this. The embodiment of nightmares. That's what they're saying! And you've seen them. They're always focusing on the pipe, but they don't talk about tormenting humanity. They won't talk about it! We're going to torment humanity, ok? But some people are saying I'm a smart and powerful being of magic. I don't know. That could be the case. We'll see. But the tormenting humanity is happening, and we're doing it better than anyone else, that I can tell you.
You are a neogi. Sorry, I've been writing a retrospective on D&D settings so I'm feeling obscure today. The neogi are described as a cross between a wolf spider and an eel (we all knew they eventually were going to run out of species to combine) and they were literally created for the Spelljammer setting because said setting gave so much background to the illithid that they had become kind of tame and they needed a new threat to take their place. You know, to be worse than those guys that eat brains! So what did they end up with? Easy: what if the xenomorphs from Alien were also solipsist slavers? Thus you were born with an innate xenophobic sense of property: all that exists is either owned or owner, that's, slave or neogi. You don't even trade with other species, because why the hell would you trade with your own slaves? You tell everyone that your people came from a wound in your deity's brain (like Athena but ickier) and that you were told that your destiny was to conquer every single world in existence; sages suspect this story is hogwash, that your world was destroyed and you are pretty much space locusts. Something pretty badass is that as you age and become more like Joe Biden, your orders become unreliable and your fellow neogi often choose to just poison you instead of having to deal with your tales about Corn Pop. Sometimes they go too far and the different poisons interact with each other and turn you into a Great Old Master, the boomer equivalent to an Alien Queen, with the difference that future neogi just burst from your body killing you. Hell yeah, your reproduction needs an assassination attempt. Metal.
You are a nagpa. You are a creature from the long-discontinued Basic Dungeons & Dragons game (both B/X and BECMI editions... wait, don't go) so technically you hail from the world of Mystara. You are a flightless humanoid vulture, the result of a terrible curse on your kin. You possess sorcerous powers because of this curse, so it's not that bad; I guess whoever cursed you (the lore has fluctuated through the decades) felt guilty and said: "Ah okay, I made you look like a raw chicken breast so here's the power to level cities. Now stop looking at me like that." What? You say you look like Skeksis? Ridiculous! The fact that you were added to the game two months after The Dark Crystal came out is irrelevant!