Last Updated on January 22, 2023
Most of D&D’s monster types are unified by a shared origin. Constructs are built creatures while celestials hail from the upper planes. Fey have their origins in the feywild, and undead are animated, once-alive beings.
Aberrations are different. Many aberrations come from the Far Realm, a place outside D&D’s planar cosmology, but not all aberrations share this origin.
Aberrations are a category of unusual creatures that have no place within D&D’s planes. Some are ancient and long-forgotten remnants of a primordial era before the Forgotten Realms’ present order.
Others are unimaginable hyper-advanced creatures, speculated to have traveled from the future. Some aberrations have origins that are unknown or unknowable, believed to be the creations of gods.
Whatever their origin, aberrations include some of D&D’s most iconic and terrifying monsters.
Many aberrations are inspired by real-world cephalopods – creatures evolutionarily and visually distant from humans that possess an alien and unimaginable intelligence.
Deep Speech and the Far Realm
Aberrations have a wide range of origins, but many come from the Far Realm. The Far Realm isn’t like other planes of existence; it’s the unknowable expanse beyond them.
The rules of this space are terrifying and incomprehensible. Visitors from the Far Realm are terrifying and alien; visitors to it return physically and mentally unrecognizable.
Deep Speech is the shared language of aberrations. This language is even used by aberrations that don’t come from the Far Realm.
Because there are so few aberrations in the material plane and because so many aberrations can communicate telepathically, Deep Speech is very unusual to hear spoken.
Mind flayers, or Illithids, are terrifying brain-devouring creatures whose empire spans countless worlds and whose terrible experimentation has warped and twisted entire races of creatures beyond recognition.
Humanoid in appearance but with tentacle-sprouting faces, much of illithids’ horror comes from their twisted familiarity. They build and conquer and use technology and magic.
Mind flayers are among D&D’s most iconic bad guys. They live in a complex society, and they have a ton of variations and related creatures, from intellect devourers to neothelids, across multiple source books.
Mind flayers are also D&D’s most notorious mind-meddlers and slavers. Mind flayers are likely to appear alongside a range of unwilling thralls, notably including duergar.
Mind flayers create unique environments around themselves. Their nautiloids – flying ships that they use to travel between worlds – are squishy and organic and cephalopodic.
The same applies to the places they inhabit – mind flayer colonies are filled with technology that is organic and unrecognizable.
Running Mind Flayers
Mind flayers are highly interdependent telepathic creatures.
Your party is unlikely to face a lone mind flayer in isolation unless it’s an outcast or a lone agent exploring new territory for its colony. Even in these cases, the mind flayer will likely have a retinue of thralls.
Mind flayers’ thralls are mind-controlled creatures to whom the mind flayer feels no attachment or duty.
These creatures will recklessly fight to the death if it provides a strategic advantage or the opportunity for the mind flayer to escape.
Extract Brain is mind flayers’ signature ability and also their most terrifying one. As an ability that instantly kills the target on success, you might want to showcase this for your players before deploying it against them.
Veteran players will know mind flayers, at least by reputation, but if your players are relatively new to the game, then allowing them to watch a mind flayer using all its scariest abilities against an NPC first will foreshadow everything they’ll be facing later on.
Mind flayers are telepathic, and it may be tempting to single out players for individual telepathic messages both in and out of combat.
While this is a useful tool, it’s best used sparingly. Particularly for long roleplayed conversations, if some players can’t engage with what’s happening, then they may get bored or stop paying attention.
Beholders and Beholderkin
Beholders are one of D&D’s most notable additions to the fantasy genre. In appearance, a beholder is a huge eyeball surrounded by smaller eye-stalks.
Beholders are paranoid, secretive, and xenophobic, hating and mistrusting any creature different from themselves.
Beholders may head huge shadowy empires of creatures they deem lesser to themselves. They’re typically solitary though. Beholders exploit, control, and manipulate, but they don’t collaborate.
There are also several creatures that fall under the category of beholderkin and may show up in similar circumstances to beholders. These include lower-CR monsters like spectators and gazers.
Beholders may appear as lone monsters, particularly if your party stumbles into their lair. Beholders aren’t naturally team players – they hate any creature different from themselves, including other beholders.
Some beholders channel their hateful energy into assembling vast organizations and empires of other creatures under their control.
These beholders are likely to be the BBEG of a campaign or a recurring NPC that the players are unable to trust.
Beholders are famously paranoid and will likely be convinced that your players are plotting against them in some way.
Are your players secretly working for the beholder’s archnemesis? Probably not, but the beholder is still convinced that they are. You can reflect this in both roleplay and in-combat taunts.
Running beholders in combat is relatively straightforward. While they have a range of possible abilities in the form of their various Eye Rays, which of these abilities they use is determined randomly.
This means you, as a DM, aren’t lumbered with deciding between all those abilities several times per round.
Aboleths are unimaginably ancient creatures that, in an era forgotten by all but the aboleths themselves, used their telepathy to influence and enslave the creatures of the time.
The aboleths were gods to these creatures, so when the gods of Faerûn appeared, the aboleths were overthrown and forgotten.
Aboleths, with their perfect memories that span generations, have never forgotten their past glory or their fall. From their watery lairs, aboleths work over untold millennia to take back control of the world.
Aboleths dwell in the elemental plane of water, ocean abysses, and deep lakes. Underdark lakes are particularly likely to be host to an aboleth.
From these places, the aboleth reaches out telepathically to manipulate creatures. Aboleths probe to find a creature’s greatest and innermost desires to tempt them with.
An aboleth encounter can make for a great side-adventure in a longer campaign.
Aboleths have a pervasive influence on places at the edge of their lakes.
Even if your players aren’t themselves contacted telepathically (which they absolutely can be!), they’ll probably still notice some signs that NPCs around them are acting strangely.
An aboleth might try to draw your party into the lake to enslave them. Just as easily, it might decide that your PCs represent to great a potential threat and try to ward them away.
Aboleths’ plans are long-term, and they’ve not survived as long as they have through recklessness. In either case though, your players will probably realize that something is going on and investigate.
An aboleth can make for an interesting combat encounter, particularly as most aboleths will have access to their lair actions in most combat encounters.
That said, aboleths are most interesting and most unique in how your players stumble upon them and how they attempt to manipulate your players prior to a combat encounter.
Aboleths are likely to have a selection of worshippers and mind-controlled minions. Kua toa colonies are particularly likely to form cults around an aboleth, so your party might face kua toa alongside an aboleth.
Slaadi are horrible toad-monsters from Limbo that reproduce in two different ways, both of which involve killing humanoid creatures.
A red slaad can use its claw attack to inject an egg into a humanoid host. This egg hatches into a tadpole, which eats the host from the inside out and then transforms into a full-grown blue slaad.
A blue slaad’s back is studded with bony hooks that carry a disease called Chaos Phage.
If a humanoid is infected with Chaos Phage, then the humanoid will gradually have its hit points reduced to 0, at which point it’s transformed into a red slaad.
In either case, if the humanoid was able to cast 3rd-level spells, then the resulting slaad is instead a green slaad.
Slaadi created by Chaos Phage are also able to transform into the humanoid they were created from.
Green slaadi, over their lifetimes, eventually undergo a transformation into gray slaadi. A gray slaad can become a death slaad by consuming the corpse of a dead death slaad.
Slaadi are a little paradoxical. They’re manifestations of Limbo and thus should be manifestations of pure chaos.
The stat blocks of all slaadi claim that they’re chaotic neutral with the exception of death slaadi, which are chaotic evil.
In their lore though, particularly in the means by which they reproduce, slaadi behavior is very obviously evil.
Their color-coded nature and hierarchy are also, in practice, strictly ordered because “weaker slaadi obey stronger ones” (Monster Manual, pg. 274).
Slaadi make more sense to view as neutral evil, or even lawful evil, than chaotic neutral. This wouldn’t ordinarily be a problem, but they’re servants of Limbo, a place that all but defines chaotic neutral in the Forgotten Realms.
Slaadi also don’t make much sense as aberrations.
They have an extremely well-defined place in D&D’s standard cosmology, they’re not from the Far Realm, and they don’t even look squiddy or Lovecraftian, so there’s no thematic tie to other aberrations.
While their place in D&D’s cosmology and their status as aberrations are both weird, Slaadi can make a great invading force for your players to fend off.
Every stage of the slaadi life/reproduction cycle can make for fantastic moments of horror description the first time your players encounter it.
Because slaadi can spread like a plague, the possibility of a slaad invasion being uncontained can have far-reaching consequences for the entire campaign world.
That adds immediate tension and stakes that go far beyond your players’ ability to survive a given combat encounter.
Otyughs are darkness-dwelling eaters of garbage and carrion with an enormous appetite that sometimes leads them in search of living prey.
An otyugh uses its squid-like tentacles to shovel refuse into its gaping, spike-toothed maw.
Like many aberrations, otyughs are telepathic. They transmit simple telepathic messages, urging sentient creatures toward their lair and toward places of ambush.
An otyugh can make for a great isolated monster encounter. If your party is exploring dark places like a cave or the underdark, then an otyugh ambush makes a lot of sense.
You can foreshadow this with the party receiving telepathic messages urging them deeper and deeper into a cave.
Otyughs are also sometimes harnessed by humanoid creatures for waste disposal, although this can lead to disaster if these insatiable creatures go underfed.
An unscrupulous city garbage collector might be using an otyugh for refuse disposal, allowing her to undercut her competition on price.
This could then backfire when there simply isn’t enough garbage to keep the otyugh satisfied and it goes looking for food.
There are too many different aberrations to cover them all in detail. Others include:
- Flumph MM
- Gibbering Mouther MM
- Nothic MM
- Grell MM
- Chuul MM
- Cloaker MM
- Morkoth VGtM
- Neogi VGtM
- Choker MToF
- Balhannoth MToF
- Berbalang MToF
- Star Spawn MToF
Aberrations and the Far Realm represent a huge facet of D&D, and you shouldn’t hesitate to use them in your game.
Some of the most horrifying, evocative, and iconic monsters in the game fall into this creature type, and there are aberrations to fit a range of purposes, from one-off encounters to campaign BBEGs.
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I played the game a lot as a kid, back in first edition. Over the past few years since 5e was released, I’ve really started getting back into it. Currently, I run a campaign online for some friends and my brothers, and we also play a side-sesh just to mix things up.