[This is an expanded/refined version of my old question: How would animals adapt to darkness-made beasts? ]

Premise: 'Beasts'/Seraphins are other-worldly intangible beings (you can't touch them, but they can touch you[edit]) that appear and reside within our world's dark places (caves, basements (if unlit) and the general wilderness at nighttime etc.) However, when exposed to some (depending on intensity) light, (only parts exposed to light, e.g., if only the arm is lit, only the arm is tangible.) They turn tangible and can be killed/harmed. However, it is very very unlikely that they will willingly stay tangible and so will avoid light as much as possible- they fear the light, in a way, as it makes them vulnerable and susceptible to harm.

They seek our 'dark places' as their own dimension is always unbearably bright- so much so that not only does it disable their incorporeal abilities; but also puts them in constant agony. There is no single surface/crevice/area in their home dimension that doesn't emit said 'blinding light'. However, they can open dimensional 'slits' that allow them to slip into our dimension- where darkness is quite abundant.

Information on 'Seraphins'


  • Seraphins appear as semi-humanoid creatures that are invisible to the human eye save for infrared viewing devices, ie. infrared goggles, scopes, etc. as they do emit infrared radiation. Concept: [Credit to: Thomas Istepanyan @Artstation]

enter image description here
The main idea is that they look semi-humanoid ie. example/concept given above- but more on the colourful side. They also have human-ish features akin to 'Titans' from Attack on titan where they go into the realm of the 'uncanny valley'.

Consumption- Seraphins do consume food- mainly animals and humans, if given the chance. Sea creatures or any creature submerged in water is an exception- they cannot enter water. (Though if a building was underwater and was unlit, they could 'slip' into it.)

Behaviour-Their main behavioural patterns is akin to that of the previously mentioned 'Titans' (Attack on titan) where they wander aimlessly seeking food, though they will ignore prey if they are 'full'. The Seraphins are quite common- You might encounter 5-10 if you are in darkness.

Danger- Very dangerous mainly due to their inherent intangibility, most animals (unless they emit light.) can't interact with them, and humans (without light.) Can't either. Because of this, if you are in the dark you are pretty much already dead if a Seraphin takes an interest into eating you. No creature really presents it any danger- excluding animals/humans who emit light and other Seraphin. However, even if you manage to make it corporeal, if it feels in danger in any way whatsoever- they're dastardly hard to kill. If, in their corporeal form, put into the food chain, they would definitely be the apex of apex predators- A dog, wolf, bear or even a couple of lions will have a very hard time killing it- if it doesn't kill you first. In danger, it can move surprisingly quickly- think maximum human capabilities. Their attacks consist of human-esc grabbing, hitting, biting and clawing.

Guns and well-made melee weaponry eg. Spears or swords (if used with skill) can be enough to kill one, though more than one human taking it on would be advisable.


  • While Intangible- Light. to be exact, if you can read in said light comfortably without straining your eyes, it should be enough to deter them (turn them tangible.).
  • Water- they cannot enter water, though they are not hurt by it. (throwing water on them when they are tangible wouldn't be effective.)
  • While Tangible-
  • Bullets
  • Fire (like many other creatures)
  • Starvation (if kept tangible 24/7 and not fed)
  • Mutilation/loss of blood (In this case, a golden ichor-like liquid)

Basically anything that will kill humans and animals, though in some cases eg. pure blunt trauma, just on a higher scale.

Question: How might Fauna (animals) adapt?

Could organisms (excluding plants- though they may also evolve to form a symbiotic relationship with some animals) adapt to emit light or would they have to rely on lantern/torch/floodlight/electrical light produced by humans for survival? [edit] More specifically, evolution leaning towards bioluminescence/chemoluminescence in plants and animals, Even more specifically just animals in general, ie. Predators and Prey (by this I mean if you talk about bio-luminescent defences for prey, for example, 'prey' will be an umbrella term for all prey) - nothing too specific like a whole species/family.

  • $\begingroup$ Those things look like twisted Warframes... O.o I agree with Agrajag. Right now question is either too broad or too POB. Fascinating though! $\endgroup$
    – MarielS
    Apr 23, 2019 at 21:51
  • $\begingroup$ You've asked about evolution of an entire kingdom - like approx 1/3 of the life on Earth, and how it would evolve over an indeterminate period. YOu're talking millions of species, can you narrow it down to make it a bit more manageable? as per: worldbuilding.stackexchange.com/help/how-to-ask $\endgroup$ Apr 23, 2019 at 22:08
  • 1
    $\begingroup$ How can something be intangible, doesn't interact with creatures, but at the same time eat, attack, or interact with those same creatures? Additionally, how common are these beasts? What are the odds I may encounter one in any given year assuming I don't take precautions to avoid them? $\endgroup$
    – Muuski
    Apr 23, 2019 at 22:29
  • 3
    $\begingroup$ "You might encounter 5-10 if you are in darkness." So you're basically guaranteed to die every time you're in darkness? How has the whole population of the planet not been eaten up within the first couple nights? (Thinking about pre-civilization people sleeping in the dark.) $\endgroup$
    – Muuski
    Apr 23, 2019 at 22:49
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    $\begingroup$ "If, in their corporeal form, put into the food chain, they would definitely be the apex of apex predators - A dog, wolf, bear or even a couple of lions will have a very hard time killing it" I like all those questions about made-up creatures absurdly overpowered, followed by the question "How does X survive this?" They don't. They die. Humanity die. Animal species mostly die. Earth enters a mass extinction period. Sea creatures and maybe bugs will survive, and that's about it. Nothing will evolve fast enough to counter them. $\endgroup$
    – Nyakouai
    Apr 25, 2019 at 9:16

8 Answers 8


I don't think bioluminescence would be the best adaptation to this scenario. A bioluminescent animal would need to emit a strong light to keep away such creatures. But other than being very hard (I don't think any known bioluminescent animal can emit so much light), it would render the animal quite vulnerable to "normal" predators.

So my thoughts about adaptation:

  • become a not-so-desirable prey: selection would probably reward small animals with high fertility (like mice), since they would be too small to be a suitable food source and anyway they would be able to quickly recover from the losses of population (even because they would face no competition or danger from bigger animals, which would be the preferred preys of seraphins). Moreover, animals that have bad taste (for the palates of the seraphins) would gain a big advantage over other animals and would become dominant

  • become a nocturnal animal: animals that are awake in the night would gain some small advantage (maybe they could have a chance to flee from seraphins, even if it seems unlikely, given the description of their powers)

  • become a partially aquatic animal: some animals would learn that under water, in the night, they're safe, so they could adapt to sleep (or anyway pass the night) submerged under water: hippos, dolphins or otters could somehow protect themselves this way. Maybe even elephants could adapt (they would pass the nights under water, keeping the tip of their trunks a bit over water to breath)

  • 1
    $\begingroup$ The partially aquatic section is the answer I would have given. Sentient life may build reservoirs of water to sleep in so they can be even more safe. Or life might never evolve out of water in the first place! The first land walkers may have only come out during the day indefinitely! $\endgroup$
    – Muuski
    Apr 23, 2019 at 23:05
  • $\begingroup$ I think it depends on when the seraphins learnt of the existence of this dimension. If they learnt about it very early, probably no advanced forms of life would have time to develop on the surface (as soon there would be enough biomass crawling the surface, it would be eaten at once). Otherwise , if they learnt about it later, maybe the land animals could find a way to adapt $\endgroup$
    – McTroopers
    Apr 26, 2019 at 8:27
  • $\begingroup$ What I was thinking is that early advanced life would probably be herbivores that come out of the water to feed on plant life with no competition during the day and then retreat into the water during the night. If one such species evolved to be sentient then they may bring "water beds" further inland to find untapped resources. $\endgroup$
    – Muuski
    Apr 26, 2019 at 15:34

You would see more species with pit organs - these would allow the animals to "see" the Seraphins in the Infra Red spectrum.

Depending on the nature of their "inability to enter water" (is it just an aversion, or does it act like a static solid object such as the floor in their intangible state?) you might find animals start living behind waterfalls, or otherwise surrounded by water

  • $\begingroup$ I would want to have pit organs. That sounds awesome, and I'd be much harder to sneak up on. $\endgroup$
    – John Lewis
    Apr 24, 2019 at 16:24
  • $\begingroup$ Static solid object, i was thinking $\endgroup$ Apr 24, 2019 at 16:40

I'd say everything we see today, just more of it.

The following just to mention a few.

Bioluminescence: A glowing sheep is just an annoying meal to the Seraphin, so I'd imagine it's mainly useful for animals that can additionally deter the Seraphin once corporeal. As others mentioned, glowing in the dark would also make you very vulnerable to traditional predators.

Additionally, if animals seek light to escape the Seraphins, it could be used by other predators for hunting purposes.

Poison and Venom: Your monsters aren't immune to poison as far as you stated, so being poisonous is a means of adapting. Nor do they need to be very corporeal to be vulnerable to deadly venom.

Passive defences: The Seraphins are incorporeal in the dark, but can touch you. How does it deal with spikes such as the porcupine, or a hard protective shell?

Camouflage: Can't hunt what you can't see, smell, hear.

Escaping: Any means of escape such as speed/endurance, swimming or flight. Nocturnal birds might be the majority of your fauna as such, other animals might gather around water as the Seraphins can't enter it.

I'd imagine anything that's dangerous, and can be made both to emit light and stick to the Seraphins would be a massive problem for them. Imagine squirting glowing sticky acid at the Seraphin, or lighting them on fire with a bit of oil.


One idea, if these creatures evolved with other lifeforms, is other lifeforms use bioluminescence to deter them.

Maybe a frog that spits or oozes it, that also has spikes. If this "beast" attempted to eat the frog, the bioluminescence would make them "tangible" causing damage or pain in the beasts mouth.

However, this ability to become "intangible" isn't really possible with know evolutional processes, therefore, you can basically make up any defense or symbiotic forces you deem fit.

I do have an issue with this though. If normal matter cannot interact with them while they are in the dark, how can they interact with normal matter to eat them? I would imagine they would need to use some kind of light to allow them to kill their target.


Animals would tend to become more nocturne.

Since your seraphins are freaked out by any light, daylight would be safe enough for fauna.

By night, animals would use much the same defenses they already do to fight or flight. While it's true that sight does wonders by day, it is not the only sense available - most savannah animals for example are better than us humans at detecting threats through sound and smell.

So, supposing moonlight makes seraphins corporeal, they would be dangerous in caves, or in the open but on new moons mostly. Caves might not have enough biomass to sustain seraphins; in the open, animals will sleep by day and keep moving at night to avoid predation.

Remember that if seraphins are extremely good at hunting they might unbalance ecossystems by overhunting. If they decimate their prey in a season, they will starve on the next season and may go extinct due to hunger. Seraphins, like any other predator, will coevolve with their prey; So they might start developing handicaps to allow the ecossystem to rebalance itself.


Spoki0 mentioned bioluminescence. Bioluminescence is an excellent defense because it allows creatures to damage the Seraphins even when in the dark, but more specifically I think a certain type of bioluminescence would be put to use. The sea firefly emits a short burst of glowing liquid that confuses predators. What you could see are animals that glow in the dark more brightly as a fear or anger response, or even just when they encounter the Seraphins.

You could also see animals capable of spraying bioluminescent fluid like a bombardier beetle sprays its boiling caustic liquid. I have one question, they can eat animals from this dimension, but can animals from this dimension eat them? If so, you could see bioluminescent animals evolving that can produce very bright light from their body followed by the glowing spray. These animals would fill an important niche keeping these things in check, and would not have much competition with other predators.

Perhaps the ichor blood could be drunk, and these creatures might gain the appearance of, say, giant ticks (I hate ticks and I am cringing as I write this), but with massive lashing claws. Despite their terrifying and unnatural appearance, humans keep these creatures as pets because they are crucial for protecting human settlements. In exchange, humans would provide shelter and take care of the young. Another thing humans can do is provide medical treatment to injured animals, so these unsettling creatures might appear perfectly normal in human society. Maybe even considered loveable, like protective dogs.

It's just an idea, and it might not work if these creatures are chemically incompatible with life on earth, but it kind of sounds cool so I just wanted to present the idea. Life evolves to fill every niche, and if these beings are vulnerable to light than they could very well lose their role as apex predators. Instead, having to deal with something that is out for their blood.


The darkness beasts could lead to the evolution of sharp-edged internal cavities filled with water, which would be used as weapons. These structures would likely be contained in similarly shaped external structure, to prevent the beasts from grabbing on to the external structure of the weapon


In evolutionary terms they don't seem to have any real advantages; the light-aversion is a severe disadvantage. Unless they have a way of sneaking up on prey animals they are not much different to any other predator. (Could they catch a rabbit, or an antelope?)

They look to be killable enough by causing them to materialise around physical objects and a specialist predator or parasite would probably evolve to trick them into doing this.

I suspect they would be preyed on by something like a firefly/mosquito which makes them tangible by flashing and bites. They may also suffer from bioluminescent fungal infections.


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