What creatures should, logically, exist in the underdark?

[atemu1234]

I know logic is an extreme stretch of what the typical definition of what the word typically means in this situation, but ponder it still:

If creatures of any type - humanoids, monsters, what have you - from D&D were to live in the underdark for long enough for evolution to take place - millions of years though that may be - what would they look like? Act like?

(I'm hoping to get a few homebrew ideas out of this thread, so if you can post anything, post it)

[Togath]

Well, pale/clear skin is a common trait of real creatures in lightless depths.
Water dwelling creatures especially, often ending up eyeless.

Perhaps a semi translucent sea serpent with visible organs and a distinct lack of eyes?

Maybe some critters would also take a cue from the deep ocean and have bioluminescence.

A cave dwelling dragon with a long glowing tongue and long lanky limbs?

The naked mole rat is another interesting subterranean animal with stretchy skin and a skill at digging.

Goblins with large forearms and hands tipped with sturdy blunt claws, with a similar flexibility to naked mole rats?

[flappeercraft]

Maybe a Subterranean Troll?

[Temotei]

A pixie might gain darkvision and maybe some antennae that grant scent. Perhaps their wings would send out inaudible vibrations that allow them to sense objects and creatures within a small radius instead of or in addition to those adaptations (blindsense). Trade out entangle for impeding stones or maybe spore field, and depending on how many other senses the pixie develops, remove dancing lights or replace it with detect poison or ghost sound, I suppose.

A spider eater might move into the underdark because there are so many spiders down there if it suddenly starts having trouble finding giant spiders on the surface. It would actually be fairly well-suited to living underground already, though the caverns it would choose to live in would have to include large chambers so it could use its flight to its advantage with its typical tactics. Its coloring would probably change.

A behir might gain slight build or even shrink to Large size (maybe even both). Perhaps reduce its land speed to 30 feet, but increase its climb speed to 20 feet (or thereabouts). Its dark coloration range would lighten up quite a bit, perhaps even including pure white into their typical colors. This might be another good species to which you could give antennae, or maybe it could develop sensory hairs on its spines or scales or something.

An ankheg might develop the ability to tunnel through rock, maybe developing a new use for its acid to aid in this.

A manticore might develop the ability to climb or hang from ceilings with its spikes, maybe in conjunction with flaps of its wings to stay close to the upper parts of cavern chambers without the danger of slapping its wings against the walls. Increase darkvision range to 120 feet (or even 180 feet to equal the range it can attack with its spikes), add climb speed of 10 feet or up its flight maneuverability to average, reduce its fly speed by 10 feet. Could also develop tremorsense, which could be cool. Or maybe it goes blind entirely and just gains really good blindsight (has to be able to hit with those spikes at a decent range).

The tarrasque gains tremorsense or blindsight in a large radius. Give it a burrow speed and allow it to tunnel through rock. Replace its immunity to fire with immunity to cold or just tack it on. Its carapace develops some sort of counter-illumination (https://en.wikipedia.org/wiki/Counter-illumination) mechanism, allowing it to hang out in large cavern chambers with a bunch of glowing fungi and such. It might develop a climb speed, as well, because why not. Increase its darkvision to 120 feet too. Sure.

Alright, I need to go to bed, but this was kind of fun to think about.

[gooddragon1]

I know logic is an extreme stretch of what the typical definition of what the word typically means in this situation, but ponder it still:

If creatures of any type - humanoids, monsters, what have you - from D&D were to live in the underdark for long enough for evolution to take place - millions of years though that may be - what would they look like? Act like?

(I'm hoping to get a few homebrew ideas out of this thread, so if you can post anything, post it)

Could be a bit cruel: Darkenghoul/Darkenghast (http://www.giantitp.com/forums/showthread.php?483633-Darkenghoul-Darkenghast-3-5-Monster) [Homebrew]
Grimlock (http://www.d20srd.org/srd/monsters/grimlock.htm) [Not Homebrew/Core Monster]

[Pleh]

Take a look at the BBC "Planet Earth" documentary on caves. It's really fascinating.

Not only do they tend to become pale, translucent, blind, and reliant on alternative senses, but also food is rare and often in small portions. Animals of deep caves evolve to live without food for long stretches of time and their metabolism makes that energy last until the next lucky drop. So many deep cave dwellers rarely bother to move unless a meal comes by, at which point they leap upon the opportunity.

Many cave dwelling creatures rely on bats and their guano. Bats are one of the few, highly populous cave dwellers that go out of the cave where food is plentiful, and come back to the caves, dropping guano which other creatures can still get their energy from.

And, yes, indeed many creatures take up bioluminescense in caves. This is usually a hunting tactic designed to trick prey into sticky webs.

Some species of fish in caves have even evolved to live in highly corrosive acid (generated naturally by volcanic forces).

Now, what the documentary won't tell you is about magic creatures in caves or the underdark. From there, all bets are off. But if you want your underdark to be themed off of real world cave ecosystems, maybe include a humanoid bat society (I know a monster manual had one) near the entrance and a collection of vermin that rely on the Bats like vermin animal companions.

Unlike what Drow and Illithid society would have us believe, squids and spiders are not prominent cave dwellers. Illithid in a setting more reflecting realism might be for deep ocean aquatic adventures, while Drow would be forest types like the other elvish cousins, except they like dark forests that have fewer birds.

Instead of spiders, consider refluffing them as worms. Same mechanics, but it could be that chilling twist that makes the party go "yeck!" when the webs they are caught in turn out not to be a spider net, but instead they get slowly dragged up to the ceiling by a worm's butt so they can be eaten.

Myconids (the mushroom humanoids) make a lot of sense for this setting. Fungi can live in the strangest of places. Sentient myconids could even function like subterranean ents.

[Kelb_Panthera]

Sometimes ya just gotta pick a nit.

Illithids and their kin are abberations. They are wholly unnatural creatures. You really don't want to look to them, or any other abberations, for examples of any kind of natural processes. They are not related to squid, octopi, or any other cepholapod beyond visually.

[denthor]

Giant cockroaches

[Pleh]

Sometimes ya just gotta pick a nit.

Illithids and their kin are abberations. They are wholly unnatural creatures. You really don't want to look to them, or any other abberations, for examples of any kind of natural processes. They are not related to squid, octopi, or any other cepholapod beyond visually.

In that case, they can theoretically exist anywhere and there's no more reason for them to live in the underdark than anywhere else. As I said, when you throw magic in there, all bets are off anyway.

You did remind me, however, of another point I forgot this morning. Even creatures with darkvision still have the mastery of fire and seem to prefer to see color than wander about in the dark just because they can see in black and white. I feel like any humanoid race that isn't specifically light sensitive (I don't mean just Daylight Sensitive) would still maintain low levels of illumination since color can be useful information when monsters might find it easier to hide if you can't distinguish colors. That's kinda the reason most animals evolved to blend in with their environment.

[Fouredged Sword]

Well, there are things about the underdark that are different than earth cave systems. First, there is food down there. Mushrooms grow to the extent they can be farmed. There are fisures between the planes that have holes to the elemental planes and allow in various forms of material. Rivers and oceans exist, as well as forests and caverns so vasts you cannot see from one end to the other even if you lit the whole space.

This means that a lot of fairly normal looking species could exist. I have a few ideas for flavorful adaptations.

Template - White Whisker

Some creatures have adapted to live in the underdark through non-magical breeding. Living in a lightless place such creatures lose their sight, but make up for it with scent sensitive whiskers that extend from their faces. Their coloration tends to bleach into pale colors, tending to white and light gray. While such creatures have a hard time distinguishing things at a distance they cannot be fooled in close quarters. Despite being blind these creatures are feirsome trackers due to their enhanced scent abilities and are sometimes breed by underdark races for just this reason.

White Whisker is a template that can be applied to any animal that normally lives in surface environments and has sight and whiskers.

The base creature loses any sight or darkvision it has.
The creature gains touchsight 5ft. The creature gains blindsense based on it's size - tiny to small 15ft, medium 20ft, large 30ft, huge or larger 45ft.
The creature gains scent if it does not already have it. The scent ability of a white whisker creature can be used out to 120ft and offers a +8 bonus to follow tracks by smell using the survival skill. When doing so the creature counts as having the track feat.

Think of the possibility

White whisker rats
White whisker rat swarms
White whisker tiger as an alternative mount for a drow matriarch.

[Barstro]

Part of this depends on how abundant nourishment is. Creatures tend to not have complex evolutions (some have actually streamlined and "devolved") due to lack of need or else wasting precious energy.

Plentiful food, or at least sustenance that is present in ways that relocation is unnecessary, could forestall the evolution of sight. Sporadically abundant food could lead to evolved blindsense, bioluminescence, or other senses to be able to locate to the food.

Go back 50,000 years. What is the food situation? Do creatures need to fight over it?
Fight for food - natural weapons develop.
Don't fight for food - then weapons don't develop and perhaps society begins.

Natural weapons lead to more carnivorous animals evolving, things get wilder. I picture camouflage, predators having darkvision, Many creatures being able to cling to walls and ceilings.

Society leads to different ideas, leads to wars, leads to weapons. Somewhere between barbarians and ancient Rome. Probably some sort of sight, bodies not made for attacking others, severe weakness to solar radiation.

[daremetoidareyo]

breathable oxygen is gonna be at a premium.

Now, you can have oodles of mosses producing oxygen from CO2, but they need sources of energy to make their biological efforts work. Photosynthesis is probably right out, and you literally can't derive energy from darkness or cold. So the only thing left is stored chemical energy: Like siderite.

But the geological production of siderite/limestone takes millions of years, so you'll need an organism that produces a source of chemical energy so that the plants can produce oxygen. I suggest delving into magic/psionics and using some sort of vermin from the elemental plane of earth that shed carbonate rich casings or siderite or sulfates or anything that holds an electron until an organism enzymatically frees that electron to produce energy for its own uses. Either that, or you use Forgotten realms' faerzes (or whatever its called) which could be regions where commensal relationships between these mosses and magical/psionic energy produce oxygen.

The problem is if you have earth elemental vermin, chances are that you're gonna have something that preys on them directly. From here you have a ton of choices, are their predators also from elemental plane of earth? Or maybe they are ethereal? or from the stupid plane of shadow? Shadow moles? Oooh. Ethereal anenomes with a taste for earth subtyped critters would make sense.

Another option is to go into crystals. Crystals are weird. They exhibit an arguable 5 of the 7 biological signs of life, and they manipulate electrons in really strange and unpredictable ways, even to modern real world science's ability to predict chemical phenominon. Some crystals produce electricity when shaken, (called piezo electric) and this discovery is what led to the invention of speakers and pick ups for acoustic instruments. So you could have mosses that grow on piezo electric crystals that try to trap living organisms to shake the crystals to produce electrons so that they can derive energy to reproduce. Another option is to have mosses that grow on piezo electric crystals that attempt to cause earthquakes, thus shaking and compressing the crystals. The former option is cool because they would probably reproduce by sporing all in the biological organisms face and hair, which they would spread to other crystal areas like pollen and bees.

[Temotei]

A basilisk might develop glowing eyes to make it so their gaze attack hits even creatures that can't see in the dark, or maybe just an esca like an anglerfish.

[Coidzor]

There should probably be lithovores and creatures that survive off of chemosynthesis or by turning various kinds of magical or mundane radiation into energy.

[Temotei]

There should probably be lithovores and creatures that survive off of chemosynthesis or by turning various kinds of magical or mundane radiation into energy.

Some kind of cave/underdark giant might be able to do that, or another variant of the troll (there are a few already that live down there, but they're not particularly interesting if I remember correctly).

Or maybe a variant grick? Plants could do it too, I suppose. Pretty much any plant-type creature.

[Thurbane]

Humans would probably evolve into Underfolk (RoD).

[atemu1234]

Okay, so I'm definitely going to make some kind of underground troll thing. Probably going to make it have four arms for good measure.