Angels were all originally part of the same race before the war in heaven, when the ones that rebelled were cast out and sent to hell. The humans on earth were similar to angels, but without the essence that made them divine. Among the angels that remained in heaven, some took a fondness for mortals and bred with them to produce mortal offspring called the nephilim. These creatures were monstrous giants that were bestial in nature and appearance, committing evil acts like cannibalism and murder. They were eventually wiped out, but the lesson learnt was that divine and mortal essences cannot mix.

However, this appears to not be the case. Devils, angels that were cast down from heaven, are still able to breed with mortals, producing cambions. The resulting offspring is still a monster, committing evil for its own sake. However, their bestial nature is internal rather than external, as they look completely human. Legends speak of the anti-christ, a being who would manipulate world governments and turn mankind to evil acts that have yet to be seen. This being would be the son of Lucifer, once the greatest of angels and responsible for the war in heaven. He now ruled hell, as he was cast into it with the angels that rebelled with him.

How is it that devils spawn monsters that look human, while the good angels produce monsters that look like monsters?

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    $\begingroup$ jusr because devils and angels are the same species does not mean they are the same species as humans. plus species is not the greatest qualifiers, a chihuahua and a great dane are the same species. $\endgroup$
    – John
    Feb 24 '19 at 14:38
  • 2
    $\begingroup$ P.S. Is it known if Satan was banished before the Nephilim were on the Earth? $\endgroup$ Feb 24 '19 at 14:53
  • 3
    $\begingroup$ what happens when an angel procreates with a devil? $\endgroup$
    – NofP
    Feb 24 '19 at 21:28
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    $\begingroup$ @BossRoss No they are both Canis lupus familiaris, or just Canis familiaris in older literature. All dogs are the same species. $\endgroup$
    – John
    Feb 25 '19 at 16:01
  • 4
    $\begingroup$ @BossRoss you're confusing species for breed. ;) $\endgroup$
    – Paul
    Feb 25 '19 at 19:26

15 Answers 15


It depends if you're wanting to be non-religious fantasy or a religious based fantasy. (AKA, based off popular views of the religious entities in question, or the actual old religious stories about them.)

Not Religious Fantasy

You can have it simply be different breeds or subspecies. Many species vary wildly across individuals (think queen bee vs worker bee or Great Dane vs pocket poodle.)

Religious Fantasy

However, if you're going religiously based, angels and demons are not directly related. Biblically speaking, they're two very different creatures (possibly different species) and nowhere in the bible does it claim they're the same. It does, however, imply that fallen angels join demons to fight along side them (although, interestingly, no demons every rise to side with God).

Before the Bible was consolidated into one book, the origin of demons was made very clear. All demons are specifically the children of Adam and Lilith, as opposed to humans who are the children of Adam and Eve. You'll notice in the bible there are two creation stories: First is the 7 days story (where god creates man and woman at the same time), and the garden of eden story (where god just puts man in the garden of eden, and then makes women from his rib.) What happened to the first woman was left out when the various works that make the bible were consolidated into one book. The first woman, Lilith, didn't care being told what to do, and refused to have kids with Adam. This angered god, who then chained her up and... well.. god got what he wanted from Adam and Lilith anyway, without her consent. However, Lilith, being so treated, made sure her kids would know exactly what she thought of God.

The children of Lilith were the 'original' humans by design. They had both from-scratch male and female, and were fully human. Eve, on the other hand, was a copy of Adam, made from his rib, and made female. So Adam and Eve's children were only half of what humans were supposed to be. Further, the serpent who tempted Adam and Eve was supposed to be one of Lilith's children (the story about it being the Devil wasn't added in until King James).

This means that Lilith's children managed to get access to both the fruits of knowledge and fruits of life before god kicked everyone out of the garden. And Genesis 3:22 makes pretty clear that's not what he wants and why. So god basically declares war on Lilith and her children.

As they're the "full" humans, fueled with both divine fruits (unlike humans which are only "half" humans with half of the divine fruits), this is where demons got there name.

The "mon" suffix as in "Human" (remember, not originally english) and the prefix "Dei" as in "Divine". How it was originally pronounced may have been closer to "Diman"

Demon literally means "Divine Humans", and are supposed to be the epitome of what humans could be, and were striving against God as a whole.

Obviously, when putting together the collection of works to make the bible, this makes demons look a better, and god look a lot worse (as forced intimacy and genocide are generally frowned on), so it got conveniently left out. However, if you want dig through all the old Jewish Midrash and more, it's referenced fairly often.

Although Hebrews at the time, when the story of Lilith got left out, still understood Demons and Angels were different species, this made things much later for later generations and Christians who picked up on the text. They tried to explain why there was such animosity between god and demons, and so it was crossed with verses about fallen angels joining demons to try and explain it away. And although it's not in the bible anywhere, that explanation has kept going through Christian tradition till modern times.

Here's a diagram if it helps: Diagram of relation between Demons and Angels, etc.

Possible exception:

Now, that said, the Bible ALSO says that mankind is made in God's image. If we interpret that a different way than Christians traditionally do (basically meaning instead of a self-portrait, that humans are God's offspring), then demons go right back into being the same species as humans, and in turn, potentially angels and nephilim (and god himself) as well. Considering the ability for all of the above to have offspring with eachother, this actually seems a moderately likely interpretation: That God, Angels, Demons, and Humans are all different breeds of the same species. In this regard, we're back to the different breeds or subspecies being what creates different appearances again.

  • 8
    $\begingroup$ I can't comment on the theology, but the linguistics is flat-out wrong: human comes from Latin hum-ān-us: the first part means "earth", as in "exhume", the second part means "connected to…", as in "Roman". So humans are creatures of earth. Demon, meanwhile, comes (distantly) from Greek daíomai, "to divide". $\endgroup$
    – Draconis
    Feb 25 '19 at 4:25
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    $\begingroup$ Good on knowing that further back origin, although you're skipping a few steps. Demon does come from divine, but divine in turn comes from division. It does mean that demon does come from division in the long run though, but it's by inheritance; divine is middle step. As for why divine came from division, that's a whole unrelated discussion. $\endgroup$
    – lilHar
    Feb 25 '19 at 16:39
  • $\begingroup$ Link to etymology here $\endgroup$
    – lilHar
    Feb 25 '19 at 16:40

Here are two creatures of the same species:

enter image description here

enter image description here

If you and most of your kin looked like the first picture, you would probably consider the second picture--10 times larger, with an un-naturally slim face, threatening ears, loose jowls, and weirdly short and dark hair--to be a monster.

Very similar underlying genetics can account for quite significant variance in phenotype.

  • 2
    $\begingroup$ Did you mean "cause", "generate", or "account for" instead of "cover for"? $\endgroup$
    – Jasper
    Feb 24 '19 at 21:11
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    $\begingroup$ So, angels would have the aspect of giant ugly trolls while demons would be human-shaped? That's certainly a nice undoing of the trope. $\endgroup$
    – Rekesoft
    Feb 25 '19 at 10:40
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    $\begingroup$ @Rekesoft Or, they get a weird mixture of traits that makes them disproportioned and deformed: if angels were extremely tall and thin with long limbs, and a half-human / half-angel hybrid got long arms from the angel parent, but short legs from the human parent, then they would end up looking like a knuckle-walker $\endgroup$ Feb 25 '19 at 13:51
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    $\begingroup$ @Zaibis Yes, the article isn't directly related to the answer, I was just including a definition for a word that not everyone might know. $\endgroup$
    – kingledion
    Feb 25 '19 at 17:32
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    $\begingroup$ Clearly the first one is the evil one, you can actually see it scheming to do bad things in that picture. $\endgroup$
    – Pelinore
    Feb 25 '19 at 19:27

First a biblical answer and then a fictional suggestion. Use which one you like!

I think the consensus of biblical scholars is that the passage about nephilim is super weird and hard to be sure about. But it seems pretty clear that it's referring to fallen angels (i.e. demons) doing stuff. As for the antichrist, in other verses (Matt 24:24, stuff in 1st and 2nd John, etc) basically any spirit that denies Christ is the anti-christ. There are theories that the antichrist mentioned in Revelation was actually Nero, who seriously persecuted Christians. See for Christians, we've been living in the end times since Jesus rose.

But yeah! For a fictional suggestion... It's a really big thing that Satan is a liar. It's so much a part of what he is that Jesus said lying is his native language; the whole war is the Truth versus the big lie. So if the demons' monsters are monsters whose very essence is falsehood, their physical form would also be constantly lying about being monsters. The other ones are honest about it, at least. But it's gonna be hard to explain why an angel following God would want to make a monster lol. Hope that helps!


Hell is a pretty toxic environment. Being there over a long period of time has mutated the demons, causing them to look different from angels and passing on changes to their offspring.


Angels still bear the blessing of good, while human and demons not.

When angels and humans breed, the interaction of a non blessed with a blessed cell messes up the appearance of the result being, while the pairs blessed-blessed or non blessed-non blessed give no issues under this point of view.

  • 1
    $\begingroup$ So, an external reflection of the internal struggle between a "divine good" nature and the "mortal original-sin"? Whereas devils give no such struggle between "divine evil" and said sin? That gives interesting potential for whether baptism and confession would 'correct' the imbalance, and restore a more natural appearance... $\endgroup$ Feb 25 '19 at 13:55

Let's start with the premise that devils are, at their essence, corrupt angels. The corruption damaged the very core of their being - in human terms, their DNA. Not all changes to DNA are destructive; most are benign. Skin color, height, and even facial features come down to DNA. In devils, the corruption they experienced caused their appearance to become that of a typical devil, mutilated and horrible.

Angel and Devil DNA appear to be compatible with human DNA, at least in the extent that humans breeding with either results in viable offspring.

The offspring of angels is powerful and terrifying to behold, just like angels. And, like angels... have no sense of morality. Angels, of course, are good at their very core; they naturally tend toward "goodness," and never think twice about doing the "right" thing. Humans, however, have free will, and the lack of a moral compass (coupled with a horrifying appearance) turns them into monsters, inside and out.

On the other hand, Devils, having suffered corruption to their very core, have very different offspring; the corruption they suffered damaged their physical looks so much that any genes contributing to looks are entirely recessive. The human genes, being dominant, take over, resulting in offspring that look completely human, or at least close enough to pass a basic visual inspection. Of course, they still suffer the same lack of moral compass, as half-devil is just half-corrupted-angel. But, as they look human, their upbringing would be much gentler than that of a half-angel, which means they would tend less to be entirely monstrous... and instead lean towards plotting psychopaths.

  • $\begingroup$ I rejected the edit - according to the asker, the offspring of angels are terrible monsters, while the offspring of devils are human-looking, but evil inside. $\endgroup$
    – ArmanX
    May 11 '19 at 4:11

First we are to assume that Angels and Devils can be classifiable by species.

Second that they are the same taxonomic species.

Third that humans are of a different species?

Clearly then the answer is that it is something external to their taxonomic definition that allows interbreeding, as (going by our definition of species) neither could successfully breed with humans.

If it is an internal, integral and automatic capacity, neither Angels nor Devils can be classified as part of a species at all because they can breed with things other than themselves, so to speak.

In summary: However it occurs, to define Angels and Devils by specie must necessarily be flawed.

It follows anyway, that whatever agent it is that makes their breeding with humans possible is altered either as integral to their displacement(from Heaven or to Hell) or as a separate function imparted to their nature, rather than that of the agent. In real world terms it's theoretically feasible to create an egg or sperm that 'pulls apart' it's counterpart and reconstitutes it in a form viable for reproduction making ad hoc inter-species breeding possible.

If we consider that what makes Angels Angels must be 'impartable' only from the Divine, otherwise the Devil would simply make himself and his Devils undevilly, it would perhaps stand to reason that an Angel cannot simply make more Angels via mating, as it is not up to them to make more divinities, but the Divine. It might follow then that it is relatively easy to make more evil, but not so easy to make more good, so to speak. Heaven has an immigration policy to uphold after all, and free passes would make a mockery of that.

  • $\begingroup$ There are some exceptions of closely related yet separate species which can interbreed and create offsprings. Mules or Ligers come to mind. $\endgroup$
    – Philipp
    Feb 25 '19 at 12:27
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    $\begingroup$ The more I read about mules the more interesting they get. Horse and Donkey don't even have the same number of chromosomes. It shouldn't be possible for them to have offsprings. Yet breeding mules works very consistently. And they aren't malformed freaks like you would think. They combine the strengths of both their parents but none of their weaknesses, making them superior to them for many tasks. Their only weakness seems to be that they are usually infertile. Applying that concept to Angel/Human and Demon/Human hybrids might be quite interesting. $\endgroup$
    – Philipp
    Feb 25 '19 at 12:47
  • $\begingroup$ yah, tbh i don't like that definition of species as it hardly works at all when confronted with actual biology, but i picked it for the purposes of the answer and ran with it :S In reality ofc cross-specie fertility has a lot more to do with ova formulation and it's error-checking system than with an arbitrary list of creatures, hence the appeal to agency a la L.Dutch. $\endgroup$
    – Giu Piete
    Feb 25 '19 at 13:45
  • $\begingroup$ Of course, mules vs hinges and ligers vs tigons give examples of differentiation between cross-breeds depending on the gender of the parents... $\endgroup$
    – origimbo
    Feb 25 '19 at 14:55
  • $\begingroup$ And there are other ways the definition breaks down: asexual reproduction, and wolves being able to crossbreed with both dogs and foxes even though dogs and foxes cannot crossbreed with each other. It’s a lie-to-children. $\endgroup$
    – Davislor
    Feb 27 '19 at 14:41

Genetic Drift

Lucifer was cast out longer ago than the common ancestors of any species on Earth that evolved to be different (and even Creationists acknowledge what they call “microevolution”), so it stands to reason that they’ve had enough time to evolve differently.

The Medievals Were Right

That is, when they thought that different environments change people, and a hot or cold climate gave nations traits like black or pale skins. At least with regard to daemons. They’ve been living in Hell and getting hit by evilon particles since the dawn of time, and it mutated them.

It’s a Curse

In many legends, the spawn of some evil ancestor like Cain or Lilith were cursed with monstrous, ugly bodies. Be careful not to remind people of legends that some race of humans were cursed with dark skin for some mythological ancestor’s crime.

That’s Not the Real Reason

Sure, that half-angel and that half-devil look different, but not all Nephilim look like that. It’s just a false assumption. Maybe they’ve essentialized their own self-image as because of their parentage, and they themselves will be shocked to meet others and find out they’re not all like that, or even that there are angels whose children look like the half-demon.

It’s Not Genes at All

Maybe they take after the form your shapeshifting parent wore the night they were conceived, or daemons get to choose whether their children will be gracile and light enough to fly, or big, strong and hard as a rock.


The first attempt was made in ignorance. They got better at it later.

The sires of nephilim incarnated (necessary as they are beings of fire, or whatever else that defies our taxonomy) into a sufficient approximation of human bodies to have their fun. On the outside, all looked fine, they functioned as well as they needed to, their bodies had no need to be self-sustainable without whatever power the angels brought with them.

Of course, such a facsimile would be considered shamefully shallow by later standards.

Apparently, God's creations are supposed to contain proper blueprints for replication, something the old angels had not considered.

Plus, as many have pointed out, the "monstrous appearance" thing may have been colorful hyperbole, and their behavior as described wasn't exactly much different than might be expected of hyperactive beings powerful enough to suffer no accountability, and "raised" in an environment of scared, unprepared small folk.



You said that celestials (either angels or devils) are made of 2 things:

  • A body.
  • Divine Essence

I propose to add third elements:

  • Angelical/Devil Essence

Celestials were neutral creatures in the past. When a celestial comes to heaven, they got "sick" or "infected" by the heavenly/angelical essence of heaven. This "disease" produce the common phenotypes of light aurora and white-feather-wings.

Instead, when a celestial (or angel) is banished from heaven and forced to live in the hell they got "sick" of the hellish or infernal essence. This "disease" produce the common phenotype of red skin, tail, bat wings, and horns in the head.

If you want, you can make each disease the cure of the another. So if an angel gets sick of hellish they cure and instead become a devil, and if a devil gets sick of heavenly they cure and instead become an angel.

Now think in common diseases as rubella and measles, if a woman has that disease and become pregnant they child are born with deformities.

The same happens with the heavenly and hellish diseases. They produce different deformities on borns. Heavenly produce grotesque deformities in the body while hellish produce more mental like diseases (psychopath like people instead of giants).

Now, your question may be: How angel-angel or devil-devil offspring doesn't bear with mutations? Very simple, you have two alternatives:

  • Divine immunity: The divine essence works as an immunity factor to the deformities of both diseases. The problem is that hybrid offspring are only half-divine, not enough to protect you from the deformities (maybe the "divine" is a recessive gene).
  • Mortal trigger: Humans has the mortal essence as you said in your question. The hellish and heavenly essences make a reaction both with the divine and mortal gene. Remember that mortal is a dominant gene (with one parent is enough) while divine is a recessive gene (both parents must have it).
    • Divine + Heavenly => Angelical appareance
    • Divine + Hellish => Devil appareance
    • Mortal + Heavenly => Giant appareance
    • Mortal + Hellish => Psychopath mind

Basically, the Divine and Mortal essence are just genes from DNA, while hellish and heavenly are diseases which change their behavior according to the divine (D) or mortal (M) gene (like some diseases which work differently on males (Y) or females (X))

Recessive gene explanation

If you don't understand this, here is an easy explanation. A male is XY while a female is XX, so, if both have at least one X, while males aren't females also? That is because the Y gene is dominant while the X is recessive. So, if you have at least one Y gene, you become male, instead, you need both X genes to become a female.


A biblical answer to a biblical question

Exodus 20:5

...I, the LORD your God, am a jealous God, punishing the children for the sin of the parents to the third and fourth generation of those who hate me

This is effectively a warning of exactly the behaviour you're describing.

The monstrous form of the demons is part of their punishment for denying god, and that shall be given to their children as well. Innocent though those children might be in their own right, they must still pay the price for the sins of their fathers.


Lets aim for genetic plausibility.

Lions and tigers are closely enough related to interbreed. But the results of crosses are different depending on which they have as a mother or father.

This is a Liger:

enter image description here

The liger is a hybrid offspring of a male lion (Panthera leo) and a female tiger (Panthera tigris).

They grow massive because the growth promoters and growth inhibiting genes are in different locations in lions and tigers

This is a Tigon: enter image description here

A hybrid cross between a male tiger (Panthera tigris) and a female lion (Panthera leo).

They don't typically suffer the same kind of extreme-growth.

So, one option might be to make angels and humans distantly related species, such that they can interbreed with humans.

But the X and Y genes of the angelic host, while similar to humans aren't quite the same. The offspring of a male angel and a female human is very different to the offspring of a male human and a female angel much like a Tigon vs a Liger.

One grows to extreme size like a liger, the other stays a normal size but has some other set of phenotypes like a tigon.

Then make it so the rebellion was fairly gender skewed.


One very simple explanation: Metamorphosis

Like a larva which becomes a butterfly, or a mosquito.

So your setting becomes an additional dimension because your anti christ can evolve to its real form

(Metamorphosis is not only for insects, amphibians and fish do it too)

  • $\begingroup$ I am not sure I understand what you mean with negative setting. Moreover the OP never mentioned the antichrist in the question. $\endgroup$
    – L.Dutch
    Feb 26 '19 at 12:00
  • $\begingroup$ I cite: "However, their bestial nature is internal rather than external, as they look completely human. Legends speak of the anti-christ, a being who..." ; the butterfly and mosquito thing should have been a joke. If I hear "anti christ" there is the mosquito in my mind more likely than the butterfly. I deleted this for clearness. $\endgroup$ Feb 26 '19 at 12:03

Scientific knowledge at the time the Bible was written would be like looking at a minor B road compared to the surface of the Earth now. Then almost everything to most people was about what we would call superstition. There are now many scientific explanations for what were called miracles then. That said science even now will gloss over and ignore those things that don't conveniently fit into it's present paradigm for fear of personal reputation. It may well be that experiments such as those performed in the Large Hadron Collider will provide at least evidence of possible alternative existence on higher or lower frequencies than we can perceive with our current accepted human senses. Until that time comes then the existence of Angels and Demons is down to a question of faith and interpretation for the vast majority of the worlds population. If there is an explanation to be found it will be in Human DNA and particularly in mtDNA I say this because there is evidence of crossbreeding between early Homo sub species particularly Homo Sapiens and Neanderthal. You might consider having your own DNA tested,can be fun to know where your family originated from at least. I think though that unless it is done on a massive scale and possibly particularly by A- blood groups there is very little chance of finding anything. I advocate mt DNA because if such mating happened then it is likely that only the females would have any chance of reproducing. Anyway enough rambling, I came across this question while browsing something completely unrelated and thought maybe I could add some food for thought.


What you describe is called dimorphism, and there are two common forms.

Sexual dimorphism. They are the same species but different sexes, sexual dimorphism can produce some pretty drastic differences, look at the angler fish the female is dozens of times larger than the male and the male has lost the majority of its organs. In other species the males are massive while the females tiny, or have drastic different appearance because one sex has display, antlers, fangs ,armor, plumage, etc.

In your case make the demons male and the angels female. the male demons have claws, scales, and horns as part of their sexual display, they are far more aggressive which is not uncommon in dimorphism. while the females are much more subdued aesthetically. This would mean that the male offspring of angels and demons look like demons and the female offspring of both look like angels. Of course this does not have to be the case. If all the male features are carried on their Y chromosome, than male offspring of angels would not look like demons, however the female offspring of demons would look like angels, of course maybe that is where the idea of succubi comes from.

Non-sexual dimorphism, sort of... There are also non-sexual forms of dimorphism, although most often what you have is is instead sexual trimorphism with females and two morphs of male, also called Alternative male strategies. One Male that looks like the female and generally acts like the female or at least sneaky instead of aggressive and another morph of male that is larger, aggressive, and visually distinct. In this case both sneaky males and females would be angels and aggressive males would be demons. This also helps create your conflict since living separately would lead to very distinct cultures. the demons would probably have to compel female offspring to remain with the demons, they would be captives, harem females in elephant seals. It might also drive each side to raid the other for fresh genetic material. You might even have a few female angels who sneak off to find demon mates, or use demon captive for... urges.

In both cases you can imagine in an intelligent species how this drastically different behavioral baselines might lead to different living arrangements. In some human cultures unmarried males live in separate villages for families. This is just a more extreme version, and separate living combined with different baseline behavior has led to drastically different cultural values and structures. in the second case, eventually this separation will lead to speciation, but you have plenty of time before it happens for the story to happen. If the speciation if further along this could even lead to female demons and female angels looking visually distinct even if they more closely resemble each other than demon males. Speciation is not a binary condition.


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