I have a scene where a humanoid monster tries to swallow another being alive, only for them to die when the smaller being rapidly increases in size through shape-shifting and tears its way out of the larger one like a xenomorph chestburster. The larger character is about nine feet tall or so but has a mouth capable of swallowing very large prey whole like a predatory fish, whereas the smaller character being eaten is about the size of an average human. After shape-shifting the character being eaten is about seven feet tall, and the character increases in size fast enough that they assume full size between being swallowed but before they get digested. Indeed, the whole reason they increase in size is they are trying to prevent themselves from being eaten, and end up ripping their way out while being swallowed. My original plan was that the shape-shifter expanding in size to avoid being eaten would end up killing the larger character as part of the finale of an action scene, in keeping with some thematic motifs of gluttony and hubris the larger monstrous humanoid has.

However, it almost seems like even if such an action was lethal, it wouldn't be immediately lethal, and the larger character would still have some time to move and fight back before they died of shock, potentially killing the other character in the process (which is not what I am aiming for). Given this, I am trying to figure out how fast it would take for someone to die from another organism bursting from their body in such a manner, assuming that the monstrous humanoid doesn't have any special anatomy that makes them more or less vulnerable to such a tactic. My primary concern is making sure the injury is lethal enough to avoid having the larger character keep fighting for a bit and kill the smaller one before dying. For example, would bursting out of the throat be more lethal than the stomach, since it could potentially damage the windpipe, jugular, and carotid?

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    $\begingroup$ How large is this creature in the end? People survive having creatures burst out of them every day, with some of the more gruesome parasites. $\endgroup$
    – Mary
    May 28, 2021 at 22:08
  • $\begingroup$ Some more information would help with answers. How large is the humanoid monster, and how large is the shifter before and after their size change? $\endgroup$
    – Alendyias
    May 28, 2021 at 23:35
  • $\begingroup$ How big is the size difference between the two beings? Can the smaller one be completely swallowed? How fast the shape-shifter changes their shape? Does the shape-shifter have enough energy to expand its size and tear the surrounding enemy's tissue? I also want to mention that your query consists of several different questions (albeit related to each other) which is not looked at favourably at WB.SE. You might want to focus on one thing at a time. $\endgroup$
    – Otkin
    May 29, 2021 at 1:43
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    $\begingroup$ Massive organ damage usually immediately takes the fight out of creatures. $\endgroup$
    – Tony Ennis
    May 30, 2021 at 15:39
  • $\begingroup$ This sort of thing? They'd probably go into shock immediately, rendering the "when do they die" question entirely moot. $\endgroup$
    – No Name
    May 31, 2021 at 0:13

7 Answers 7


Death is instantaneous.

The damage comes not from the ingested creature clawing or bursting its way out through the larger creature's body, but from this bit:

when the smaller being rapidly increases in size through shape-shifting

The ingested creature rapidly expands, compressing the larger creature's lungs, heart, and internal organs. This causes blood pressure to spike to many times normal safe levels, causing instant ruptures throughout the big guy's vascular system, including the arteries of the brain.

The big guy promptly dies of many,many massive simultaneous strokes and aneurysms.

If it was more like the original chestburster in Alien, that took several days to grow and inflicted its exit damage via jaws, claws and acid, then there is even a chance the victim could survive, with prompt medical intervention to stem bleeding. But your chestburster is a size-metamorph, and that shines a totally-different light on the matter.


Exit thru the back.

Chest bursting. SO tired, you know. Been done, been done.

Rather than exit from the front Alien style, have your shape shifter exit through the back of the organism that ingested it. A vertebrate body plan usually has the spine and aorta behind the digestive organs. Bursting thru those would be unusual, spectacular and very quickly lethal.


If you punch a large hole in an organism, they are going to bleed out pretty quickly. The bigger the hole, the more vascular tissue they damage, the faster they will bleed out.

You get bonus points if your chest-burster grows spread out instead of in a big single ball.

Imagine the chest-burster growing inside the host with its legs spread open rather than curled up tight, then violently pulling them together before making an exit, causing internal lacerations all along the way.

An additional benefit is a single large growth would be more noticeable than a distributed growth.

Massive bleeding can rapidly drop blood pressure and make it hard to do anything other than stumble to the ground and lose consciousness.

EDIT: It is also worth considering that your chest-burster can have a mechanism to paralyze the host to minimize the risk of damage while being born.

Perhaps your chest-bursters could release a neurotoxin when they jump out?

  • $\begingroup$ maybe the chest-burster first causes massive internal damage, then waits out the ride inside the dying host, and only comes out when the victim stops squirming? $\endgroup$ May 29, 2021 at 0:39
  • $\begingroup$ why do they never exit through the side... $\endgroup$
    – user253751
    May 29, 2021 at 19:44

If you are alive inside the guts of any vertebrate, and you have the strength to burst out of a rib cage, then you can kill the "host" pretty much instantly just by ripping up its heart. Loss of blood pressure gives the host time to look surprised, clutch it's chest and fall down before losing consciousness.

The main limitation on this process is the time it takes for you to find and destroy the heart. Ripping your way out of the GI tract is going to cause extreme pain, so from the outside the likely scenario is that the host screams in pain, curls up in a ball, and is unconscious before anyone nearby can bend down and say "What's the matter?".

Don't come out through the ribs because that is definitely doing it the hard way. The easiest way out is through the abdomen below the ribs. However unless you are very careful you will find yourself coated in the semi-liquid contents of the large intestine, the primary job of which is to scavenge water from the waste food before it is excreted. You will also have to fight your way out from whatever clothes the host was wearing. If you are still small enough you could avoid the clothes by coming out through the neck or mouth.


How fast would it take someone to die from another organism bursting from their body?

Have you heard about something called mammalian birth?

It happens all the time. A child is not part of the mother, contrary to some folk-beliefs. The child gets half its DNA from the father and half from its mother. It is not an exact copy of either and has its own unique identity.

A child is an extremely efficient parasite that grows inside another creature after being implanted by a virus called "sperm". It feeds off its 'mother' and like a cuckoo gets fed and brought up by its 'parents' by a very clever strategy of manipulating their hormones so that they 'love' it.

It's survivable for the mother but there is always a risk of her death if things go wrong.

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    $\begingroup$ And more interestingly, a C-section is literally a surgically managed "chest burster". $\endgroup$
    – Graham
    May 29, 2021 at 18:34
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    $\begingroup$ The difference being the human body is built to survive the fetus coming out of that hole, rather than a much larger body ripping through parts of the body that were not intended by evolution to be ripped through. $\endgroup$ May 31, 2021 at 5:28

It really depends on the relative sizes. It would be horrifically painful having a creature rip out of your stomach, but women routinely survive similar things with a caesarean section, and go on to walk about.

If you want them to die, have them rip the humanoid in two. That would cause enough trauma to disable most people.


What goes through the whole abdominal cavity? The aorta. Cut that and their blood very quickly ends up everywhere rather than going to the body. Blood circulation stops, the brain shuts down a few seconds later. Fast enough for you?


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