Is there an iconic monster or creature for each alignment?

Question

In my D&D 5e game, I have a custom cosmology, and I'm currently working on a concept for an afterlife plane where any sentient creature who enters is sorted by alignment and guided to the afterlife. While in this afterlife plane, a character begins to take on a form that represents its alignment. This visually distinguishes each alignment from one another (making them easier to sort) but also provides a cool transformative aesthetic that my players have expressed interest in seeing.

In order to prevent this from being opinion-based, answers must entail specific monsters that have canonically been declared to be representative of their respective alignment, or creatures that have another narrative connection with their alignment or alignment-based plane. I will accept any creature from the history of D&D and Pathfinder as long as you can cite its close ties with its respective alignment.

I understand that there may be more than one correct answer (for example, Monster X may be the perfect NE monster in D&D 4.0 while it might be Monster Y in Pathfinder. An answer is considered correct as long as it is backed by the lore of its system.

Answer 1

In AD&D, the cosmology of D&D which had gradually developed over the course of numerous publications was codified into the Planescape setting, which focused on adventures on the planes besides the Prime Material. The architecture of the cosmology focused on the “Great Wheel,” the sixteen planes surrounding the Outlands. These seventeen planes, collectively known as the Outer Planes, were the provinces of belief: mortal belief became solid matter in the Outer Planes, so that each was made from belief.

Being literally made from belief, the Outer Planes were all about alignment. The Outlands is True Neutral, and then eight of the planes correspond to the various non-neutral alignments. The remaining eight fit in between the others, creating spaces halfway between the various extremes of alignment (so Arcadia lies between LG Celestia and LN Mechanus, and is thus Lawful and Good-ish-but-not-quite-truly-Good).

Each of the planes matching an alignment also spontaneously gave rise to its own “exemplars,” creatures formed of that plane (and sometimes the souls of mortals who ended up there in their afterlives, though the exact process is full of caveats and exceptions and beyond the scope of this answer). The exemplars didn’t merely “believe” in an alignment, they were literally that alignment incarnate.

The nine exemplar races, then, are:

• Lawful Good archons from Celestia

• Neutral Good guardinals from Elysium

• Chaotic Good eladrin from Arborea

• Lawful Neutral modrons from Mechanus

  • Worth noting: the modrons produce inevitables, constructs of pure law like maruts. Inevitables are not living things and do not form spontaneously and directly from Mechanus itself. Modrons are rather robot-like, but are in fact living outsiders.

• True Neutral rilmani from the Outlands

  • Extremely obscure and very, very little is known about them. Even in Planescape they were rarely mentioned and extremely rarely had any effect on history.

• Chaotic Neutral slaadi from Limbo

  • Common slaad are all colored frogs, and their color denotes their variety and powers. This consistency is a notably Lawful trait imposed upon them by their sovereigns, who used the Spawning Stone to permanently fix the slaadi in this form to limit them and prevent them from becoming powerful enough to overthrow the Slaad Lords. The Slaad Lords themselves are not frog-like, and indeed can chaotically change themselves significantly. One even did a stint impersonating Primus, the top of the modron heirarchy, in an attempt to spread chaos to lawful Mechanus (or maybe just for a laugh; hard to say with slaadi), though this damaged him significantly.

    • It is likely that all of this was made up just to make the Chaotic races reasonably approachable; after all, they had to give stats for these things. Kinda hard to do that if each and everyone is completely random and unique.

• Lawful Evil devils from Baator

  • While the LE exemplars are generally called “devils,” in particular the ruling class of Baator are the baatezu. Not all devils are baatezu, and in particular, the ancient baatorians, rather than the baatezu, are the original, in some ways rightful exemplars of Baator. The baatezu’s status as usurpers in such a lawful plane causes them many problems (which are, of course, carefully hidden by the most powerful baatezu from everyone else), including the mess with larvae and their constant need to manually purchase mortal souls. But so long as they remain strong enough to overcome these problems and any who would take Baator away from them, Evil recognizes their might makes right and they can bend the plane to their needs and produce more baatezu. The ancient baatorians had largely vanished from the plane before the baatezu even got there; what became of them is one of the greater mysteries of the setting.

• Neutral Evil yugoloths, or daemons, of Gehenna and Hades

  • Gehenna is the plane between LE Baator and NE Hades, and yugoloths were originally from there, rather than Hades. The near-mythical General of Gehenna specifically “purged” the yugoloths of law and chaos with an artifact known as the Heart of Darkness. They now naturally form in both planes, making them the true exemplar of Hades, and they are neutral evil, but some caveats seemed worthwhile. They now mostly operate as notoriously unreliable mercenaries, always open to higher bidding from those they were hired to fight.

  • Like the baatezu and tanar’ri (below), yugoloths are not the original exemplars of neutral-evilness. The ancient baernoloths, who were the original exemplars, specifically created the yugoloths to replace them, to be the most perfect exemplars of pure evil.

• Chaotic Evil demons of the Abyss

  • Just as with the other evil exemplars, the current demons, the tanar’ri, are not the original exemplars of chaotic evil; the obyriths were that. The tanar’ri overthrew the obyriths towards the end of the War of Law and Chaos.

And if you’re wondering, yes, there’s a reason the Upper Planes didn’t get any sub-notes: they just never got a lot of attention. They always existed, and had some history and description, traits, stats, and so on, so they aren’t pure mysteries like the rilmani, but they also just don’t have a lot going on. Things are fairly peaceful in the heavens, as it turns out. However, while we’re on the subject, there is one thing about the Upper Planes that does warrant a mention: angels. Angels are not exemplars, and can be any good alignment (barring a fall, of course), but they are in some ways above the good exemplars. They are much, much more powerful, and represent all of Good. They are the direct hands of the good gods. Other alignments lack any similar “arch-exemplar.” So the heavens do have that going for them.

The Great Wheel cosmology was re-used throughout many editions of D&D, though significant changes were made from time to time. Third edition, and the 3.5 revision, largely kept it, except in the new Eberron campaign setting which completely eschewed it. Fourth edition nominally used... something sort of maybe like it, but mucked with most of it. Fifth edition once again is using Planescape as an official published setting.

Answer 2

The methodology I've settled on is as follows:

• The creature is the dominant inhabitant of the correct alignment plane (according to the Manual of the Planes). The Greyhawk (default setting for D&D 3.5) cosmology lists the Outer Planes that are keyed to the nine alignments.
• The creature has the appropriate alignment subtypes - an iconic Lawful Good creature is both (Lawful) and (Good). A neutral creature obviously doesn't need to be (Neutral) because that doesn't exist.
• The creature is strong. Wouldn't it be lame if the ultimate destiny of your soul is... being shaped like an imp?
• The creature is not obscure, appearing in the core books of D&D 3.5 and throughout the history of D&D. A creature can't be iconic if it's buried in the Dusty Tome of Whatever.

Lawful Good - Trumpet Archon

Mount Celestia is the plane that is in equal parts Lawful and Good. Its native sons and predominant denizens are Archons - angelic beings of Law and Good that are sent to battle evil throughout the planes. There are many kinds of archons, but of the ones in the Monster Manual, the trumpet archons are the mightiest. They hearken all the way back to the very first Manual of the Planes published in 1987, meaning they're older than a good chunk of people that play the game!

Neutral Good - Leonal

Elysium is the plane of pure Good, balanced between Law and Chaos. Its dominant inhabitants are called guardinals, of which Leonals are the strongest in the Monster Manual. These guys hearken back to 1995. Surprised that angels aren't here? Turns out astral devas, planetars, and solars are spread evenly between the Good planes (alignment: always good (any)), rather than being properly Neutral Good.

Chaotic Good - Ghaele Eladrin

Arborea is the plane of choice for Chaotic Good beings, and eladrin are the Chaotic Good beings of choice for D&D. Manual of the Planes literally says that ghaele are the "best known" of the eladrin (p. 145) so there you go. They go back to 1995 like the leonals.

Lawful Neutral - Marut

The most Lawful plane in the cosmology is Mechanus. The MotP describes Inevitables as their primary residents - beings so Lawful that they go around enforcing the laws of the universe! The oldest (and strongest) of these is the Marut, who enforce death. They appeared in 1987 alongside archons. Technically, Modrons are older Lawful creatures, appearing in 1983, but they got almost no attention in 3rd and 4th editions.

True Neutral - Tarrasque

This is sort of tricky - the Outlands are more of a meeting ground for planar powers than a thing in its own right. The Rilmani are described as the True Neutral outsiders in a few obscure books, but they hardly have the notoriety to be called truly iconic. Creatures that are too dumb to have ethics and morals are also True Neutral, so you could pick the Tarrasque (the biggest, baddest of the beasts) as the paragon. He came out in 1983 and is an iconic high-level enemy. He's not iconic for True Neutral, but he's the most iconic creature that is True Neutral, for what that's worth.

Chaotic Neutral - Gray Slaad

Slaadi are the best-known monsters of Limbo, the plane of true chaos. The MotP says they have been natives "since time began" (p. 94). The slaadi are so iconic that they are product identity of Wizards of the Coast, and not licensed out as part of the Open Game License. Introduced in 1981, these frog-like outsiders are even older than the archons.

Lawful Evil - Pit Fiend

When it comes to the kings of Baator, there's only one race that rules over all others in the Hells. Devils! Baatezu! By any name, they are the iconic Lawful Evil beings - fighting the Blood War on the side of Law, and causing Evil acts in the world. Pit fiends are the generals of Baator's mighty armies. They are both the strongest beings I've listed so far, and the oldest, appearing as far back as 1977.

Neutral Evil - Night Hag

The Gray Waste of Hades is where the Blood War between Lawful and Chaotic Evil takes place, so there's not a lot of iconic creatures here that are still alive. Yugoloths (or daemons) live here but they are from Gehenna, a different plane. These guys were never really popular, unlike Night Hags, who appeared in 1977's Monster Manual and were said to rule in Hades. The hag is also substantially distinct from demons and devils, which is a nice bonus.

Chaotic Evil - Balor

If the devils are classic LE, demons (tanar'ri) are classic CE. They go back to 1976. Ruling the Abyss, the quintessential Chaotic Evil plane, demon armies are led by the Balors into battle against devils, in the eternal Blood War between law and chaos.