What happens when a unicorn wanders to Gehenna? Or a wyvern spends a summer in Mount Celestia?

In Planescape: Adventures in the Multiverse, you'll not only encounter a myriad of brain-breaking creatures but find rules for customizing monsters exposed to one of the Outer Planes. These can be used with optional rules found in the Dungeon Master's Guide that show how the Outer Planes may affect a creature.

Let’s explore three of the Outer Planes and see how they can completely change a creature's appearance, attitude, and abilities:

• The Beastlands: Nature Unbound
• Mount Celestia: Seven-Layered Heaven
• Gehenna: The Heights of Greed

The Beastlands: Nature Unbound

You know that old cliche about a family pet dying and the parents telling their young kids that the pet went to live on a “farm?” Well, in the world of D&D, that’s actually not too far off from the truth. But it's not so much of a “peaceful upstate farm that you can never visit.” It’s more of a sprawling plane of untamed wilderness that forever calls to the chaotic but pure nature of all living creatures.

In the Beastlands, you’ll find the very essence of nature distilled and permeating every ounce of organic matter. Plants and animals grow into platonically ideal versions of themselves. Some grow into even bigger, more fantastical versions of their natural selves but still somehow maintain balance in this unnaturally natural world.

Traits of Creatures Influenced by the Beastlands

Stripping away the artifice of civilization is one of the core concepts at the heart of the Beastlands. The primeval energies of this plane may bring out a creature’s instinct to hunt (or avoid being hunted), granting them advantage on Animal Handling, Perception, and Survival checks. Some also gain the ability to see invisible creatures or objects and even maneuver across terrain without leaving tracks behind. Whatever boon is bestowed upon them, a visitor to the Beastlands may quickly discover whether their inner animal is predator or prey.

Many plants and animals of the Beastlands are awakened, granting them the ability to speak and think like humanoid creatures. But some creatures may just spontaneously gain the ability to verbally communicate with plants and animals just by being on this plane for an extended period of time.

Creatures may take on bestial aspects while in this Outer Plane; their canines may elongate, or they’ll grow a magnificent mantle of back and shoulder hair or sprout a prehensile tail. If you want to play a shifter in the Forgotten Realms, your character’s abilities could be the result of them being influenced by the feral energies of the Beastlands. Maybe they were left there as a baby and raised by awoken animals, like a certain loin cloth-wearing, vine-swinging, “ape-man” who’ll always be in my heart…

How to Adapt Creatures to the Beastlands

When adapting a creature to be influenced by the Beastlands, consider the creature's natural abilities and how those abilities could fit into an ecological niche.

Feral Quicklings

Quicklings are tiny, chaotic speedsters. A band of quicklings influenced by the Beastlands could sprout feathers and long, raptor-like talons and develop into tiny fey clawfoots. Using their incredible speed, they may snatch eggs and avoid capture. Their tiny, razor-sharp claws, meanwhile, could make for a pesky and potentially deadly encounter.

Awakened Fungus

Fungus is an extremely important part of any ecosystem. It’s essential in breaking down organic matter and returning it to the soil. Maybe your players hear a childlike scream for help echoing from the bottom of a deep, dark chasm. But when your players find the source of the scream, they discover it's an awoken fungal colony of shrieker mushrooms and violet fungus. The shriekers act as bait, while the violet fungi kill the prey, feeding the colony.

Bestial Beholders

Even something as antithetical to nature as an Aberration can be shaped by the powers of the Beastlands. A wayward beholder has crafted a secluded lair, where the Beastlands have slowly transformed it, giving it strange arachnid-like qualities. Here it's spun a lair made out of webs, sporting a menagerie of petrified victims, frozen and ready to be consumed whenever the beholder wants a little treat.

Mount Celestia: Seven-Layered Heaven

Artist: Brian Valeza

The towering testament to the power of goodness, a shining beacon of aggressively chill vibes. You are going to behave yourself whether you like it or not, ya hear? Mount Celestia is where goodest of the good celestials hang their hats and hearts. It is composed of seven perfect plateaus, each more exclusively good than the last. It is home to angels, couatls, and unicorns; I hear even Bahamut, the Platinum Dragon, has a house there. Any evil, or even mildly jaded, creature experiences an unmistakable dissonance upon entering this plane. The Outer Plane's healing light can remind even the most corrupted creature that every ounce of kindness in this universe matters.

Gifts Given to Creatures Influenced by Mount Celestia

Mount Celestia acts as a beacon to the Outer Planes; a stalwart beam of light forever piercing the darkness and empowering the good. Its power seeks to amplify the light within its righteous denizens and enkindle embers of goodness in even the darkest of hearts.

A creature influenced by Mount Celestia may take on a beautiful metallic sheen, sprout angelic feathers, or get really into yoga and crystals. Some creatures start to shed casual radiance, glowing with a bright light in a 10-foot radius that they can turn on and off. This place is so inherently good that good-aligned creatures can be granted the benefits of the bless spell just by walking around Mount Celestia.

If a creature influenced by this place dies in battle, it may even release a glowing orb capable of healing any nearby good-aligned creature.

How to Adapt Creatures to Mount Celestia

When Mount Celestia influences a creature, it finds whatever good it can be capable of and then compels it to serve that goodness. When adapting a creature to be influenced by Mount Celestia, consider what makes that creature special and how that feature or trait can be used for the greatest good imaginable.

Sparkling Puddings

A black pudding that’s been influenced by Mount Celestia may take on a sparkling, molten gold-like appearance. Its acids may no longer corrode metal, wood, or organic matter. Instead, it now heals any creature it touches for 1d8. Its touch may also have the properties of the mending spell, repairing or resetting any inorganic material to its original, intended state.

A Kindness of Ravens

The divine light of Mount Celestia could transform seemingly mundane animals into living spells. A flock of ravens influenced by Mount Celestia could take on golden spectral shapes, transforming them into a living mass cure wounds spell that seeks out specific individuals, or anyone or anything that needs healing. Technically a group of ravens is called an “unkindness,” but not on Mount Celestia.

Helpful Hulks

A mist hulk influenced by Mount Celestia could be a brilliant, white figure made of fluffy cumulus clouds, dutifully redistributing water vapor from the bottom plateaus to the top. Its hideous wailing could instead be a soothing whisper, refreshing weary travelers or wounded soldiers.

Gehenna: The Heights of Greed

You can easily get a good leg workout traversing the endless inclines of the volcanos found in Gehenna, and that is the only nice thing anyone can say about this wretched plane of avarice, paranoia, and selfishness.

This neutral to lawful evil plane is the heart of all selfish thoughts and deeds within the multiverse. It is the birthplace of all yugoloths (which explains a lot if you know anything about yugoloths). The entirety of the plane rests on several volcanos, forcing anyone who traverses it to climb or descend at a 45-degree angle the entire time. Unlike Mount Celestia, which has seven, even plateaus, no one stands equally on the surface of Gehenna.

Its denizens are eternally trying to keep up with the Joneses in the most nefarious way possible, doing whatever they can to ensure they have the biggest pile of baubles or volcanic vents on the block. The most important residents live at the highest points of the peak, which is also the rim of active volcanos (which I guess is a big flex for them? Seems like an insurance liability to me, but whatever).

Competition Unleashed

Gehenna did not come here to make friends, Gehenna came here to be number one! Any creature attempting to use magic to aid another must succeed in a DC 10 Charisma saving throw, or else the spell automatically fails. And even if a healing spell does succeed, a resident of Gehenna may radiate a vitality-sapping aura, sucking up half of the regained hit points for themselves (I… drink… your… HIT POINTS!).

The single-mindedness inspired by Gehenna twists those who walk within it into gangly, exhausted-looking monsters with long crooked limbs and giant vacant eyes, good for ogling their precious hoard. They may even gain a preternatural ability to sense the location of precious stones and metals.

How to Adapt Creatures to Gehenna

When adapting a creature to be under the influence of Gehenna, think about what the creature naturally seeks out and then amplify that need times a thousand. Imagine how this creature’s appearance and behavior can be warped by complete and total selfishness.

Unhappy Harpies

A harpy matriarch influenced by Gehenna may make a large nest near the top of one of Gehenna’s smoldering peaks, made of twisted metal, brambles, and pumice stones. But adventurers probably won’t find any eggs in these nests, just a hoard of baubles. The harpy employs its eerie song to magically entice weary adventurers to march up to its nest and relinquish their treasures (before the harpy eats them or pushes them into a volcano).

The Condescending Cruelty of the Androsphinx

An androsphinx influenced by Gehenna may see its cat-like body grow long and spindly, its ribcage protruding beneath its haggard wings. Its once inscrutable face now hangs with an unmistakable look of contempt. It may be utterly obsessed with guarding its precious secrets by luring interlopers into nigh-unsolvable riddles or trials, like the Jigsaw of sphinxes.

Jaded Couatls

Couatls are some of the most selfless entities in the multiverse, and have been since the dawn of time. They’re incapable of telling a lie, and they seek out individuals of importance and guide them on the right path. But what happens if a couatl is tasked with waiting in Gehenna for a specific individual, and said person never arrives?

Perhaps the powers of Gehenna wither their brilliant wings and drain them of color, turning them more into feathered claws than wings. Whatever quest they’ve been sent on quickly dissolves in importance, as they grow bitter and jaded. Their inability to lie warps into an inability to tell the truth. They still seek out individuals with great and good destinies, but only to lead them away from their divine callings so they too can become stranded shadows of their former selves, slowly rotting on the slopes of Gehenna.

Have Fun With Far-Out Ideas

Adapting creatures with planar influences opens up so many new stories you can tell as a Dungeon Master. Using the mechanics and ideas presented in Planescape: Adventures in the Multiverse and the Dungeon Master's Guide, you can throw some incredible narrative curveballs that can shock and intrigue even your most seasoned players.

So, go ahead! Make a soft-hearted chain devil daddy from Mount Celestia! Or a froghemoth with an inferiority complex from Gehenna! Or even a feral flumph from the Beastlands!

Kyle Shire (@kyleshire) is a contributing writer to D&D Beyond and a producer for Critical Role. In the past, he worked as a producer, writer, and host for Machinima Studios and Warner Brothers Interactive Entertainment. He's appeared on HyperRPG as the Mayor of Kollok and the Saving Throw Show. He currently lives in Los Angeles.