There are a number of stories that contain a being that can turn parts of itself intangible at will, meaning it won't interact with most objects:

  • The twins from the second Matrix movie;
  • The demon from Kim Harrison's first Hollows book;
  • Kitty Pryde from X-Men.

This seems to make physical defenses useless: a shield won't stop a being that can just make part of their arm go straight through the shield. A sword attempting to cut off a body part will just go straight through the body part without doing any damage. A wall or a door won't stop it either because it can just phase through.

For this question, assume the following properties:

  1. The attacker can make any or all parts of his body intangible at will, for any length of time. Intangibility means it does not interact with any baryonic matter, whether living or inanimate. The process that causes the intangibility is based on fictional science and is not of magical or supernatural nature.
  2. The attacker can still "walk" on any surface that a tangible person would be able to walk on, as well as on the air.
  3. The attacker can have an intangible bit in between two tangible bits.
  4. The attacker can still eat, drink and breathe and has full sensory perception, even if the sensing body parts are intangible.
  5. Anything the attacker wears or wields can also be turned intangible, following the same rules, as long as he touches it. So he can't fire a projectile through a solid wall, but he can shove his gun fully through the call, fire it and then retract it.
  6. The setting is modern times to near future, with currently no power dampening tech available.

How would one defend against such a being, be it through preparing the location where the confrontation will be or through specialized armaments and training?

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    $\begingroup$ What's this being's goal? Is there any reason for it to expose itself by becoming tangible at all? It seems the best defense would be to just remain completely incorporeal at all times. It could still interact with the world just by wearing a pair of corporeal gloves that could be phased in/out at will. A lot of the answers are focusing on gas - will that affect the being or not? The notion that it doesn't interact with any matter is very much at odds with its ability to breathe. $\endgroup$ Nov 25, 2019 at 15:39
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    $\begingroup$ Does this individual interact with energy? For example Shadow Stalker in Worm, whose powers are disrupted by electric fields. Does the intangible state make them immune to gravity, as they cannot interact with baryonic matter? $\endgroup$
    – nzaman
    Nov 25, 2019 at 19:29
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    $\begingroup$ I would advise you to impose some constraints on this power, since right now you're nearing Superman levels of strength, which is a problem unless you want a basically all-powerful hero. I would favor time and/or energy constraints, personally: limit how long they can go intangible and/or how often they can do it before exhaustion sets in. This would compel them to use their brains; sure, you can hide in a wall for a few seconds to dodge the guards, but you trivialize your story if the hero can walk through every wall in the Pentagon to whatever secret documents and take them out the same way. $\endgroup$
    – Palarran
    Nov 26, 2019 at 1:33
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    $\begingroup$ "Intangibility means it does not interact with any baryonic matter" directly contradicts "The attacker can still eat, drink and breathe and has full sensory perception", all of which require interaction with baryonic matter. $\endgroup$ Nov 26, 2019 at 11:39
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    $\begingroup$ If the attacker can "walk on the air", does that mean he has no mass while intangible? If so, shouldn't he be in zero-G anytime he's fully intangible? That part doesn't seem consistent to me. $\endgroup$ Nov 26, 2019 at 14:47

13 Answers 13


"4. The attacker can still eat, drink and breathe and has full sensory perception, even if the sensing body parts are intangible."

Assuming based on their other immunities that they would be unaffected by airborne agents while intangible. Assaults on the other senses should work. Flashbangs, Sonic attacks, Bright lights. Attacks on their fully perceptive sensory organs should yield deterrent and if enough energy is pumped into them this way could be a bit more than that by causing Blindness, Deafness or internal bleeding from ruptured organs such as eardrums.

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    $\begingroup$ A strong-enough shock to the senses can trigger an involuntary reflex response. It's possible that such a response could make the creature lose concentration and re-materialize for a moment, allowing you to counter-attack it by conventional means. $\endgroup$
    – bta
    Nov 26, 2019 at 19:57

Raising the Cost of Interaction

When such a being is intangible, it can't interact with anything in a useful/harmful way: it must make at least part of itself tangible to be able to cause harm. So, make the act of becoming tangible extremely costly and dangerous.


Strong ionizing radiation can cause immediate and invisible damage to living tissue in the area. Bathing an area in such radiation can cause severe damage to an intangible being the instant it decides to become tangible. Even if it only makes a part of itself tangible, it can sustain serious injuries before it even realizes that something is wrong. In this instance, a soldier would either need protective clothing (which could give away the threat), anti-radiation meds (much less effective than blocking the radiation altogether), or a death wish.

Non-ionizing radiation (such as RF or microwave) can cause thermal effects: it can literally cook living tissue. While this can be more immediately noticeable than the damage caused by ionizing radiation, it can also be used as a directional weapon. Large, ground-based antennas used for communicating with satellites can emit this type of energy in a specific direction.

Nowhere to Hide:

If the being's control over its power is too great to rely on it ever becoming tangible, then you must strike at it while it's intangible.

Carbon Monoxide:

Invisibly deadly, an entire facility could be filled with CO without the target ever realizing it. Even though they're still able to breathe while intangible, they need something to breathe. If all that's available is CO, then they'll be dead before they've taken a dozen steps towards their destination. Soldiers within the effected area could theoretically be given implants which allow them to survive within the CO for a short while (essentially, air supplies which can be hidden under clothing, and connect to the user's airways in a way that's not obvious). This is science fiction, but could reasonably be created with technology not much more advanced than what currently exists.

Alternatively, soldiers could be armed with weapons that emit CO (like a spear that pumps car exhaust out of holes along its haft). If these weapons are stabbed into the lungs of the intangible being, they'd instantly displace the atmosphere in that immediate vicinity with carbon monoxide, causing injuries right away.

Explosive Decompression:

If the being needs air, then they'd theoretically need that air to exist within a specific pressure range, like a regular human would. That being the case, rapidly exposing them to negative pressure would be immediately and violently injurious. Sticking them in a vacuum chamber probably wouldn't work quickly enough to prevent escape, but a thermobaric bomb could likely do the trick as long as you don't mind all the collateral damage.

  • $\begingroup$ I agree. No-matter radiation, (electromagnetic) fields and too much energy, along with deprivation of vital input is the killer here. The being has to be susceptible to force of some kind. $\endgroup$
    – Sebastian
    Nov 26, 2019 at 20:15

Radar-linked auto-guns.

The radar lets you know which parts of him are tangible and the guns perforate those parts with bullets.

This does require some kind of visual identification unless the entire area is a kill zone. Or simply program the gun to auto target any one who starts having pieces going intangible.


Through the power of science!!!

You said "The process that causes the intangibility is based on fictional science and is not of magical or supernatural nature."

If this is true, then that means this phasing is a physical process of some sort, one that a human body is able to generate and maintain.

Since this process is not magical or supernatural in nature, then it must be some natural (non-magical, not supernatural) process that can probably be replicated. Since it is (presumably) a human body producing and sustaining this process, then it must not require a tremendous amount of energy to sustain.

So since this is (probably) a physical process, it is very likely that we could find a way to observe it - specifically the method behind it - beyond simply saying that it's phased now and it wasn't before. And since this process is able to be generated and then sustained by the energy within a human body, it is well within our means power this process with technology rather than biology, if we can just learn how the process works!

Assuming that this power is not unique, that you are able to find someone with this ability who is willing to cooperate, and that you have sufficient funds for this, it would be easy (I'd go as far as to say trivial) to find a physicist or other notable researcher willing to study this ability. It would be even more trivial to then script this scientist or research team (you do get to decide this, after all) to make a breakthrough (they're brilliant!) and gain a significant understanding of this process!

And at that point, you now have both an understanding of the process, and sufficient power to recreate it! All you need then is a little more research and a little bit of hand-waving (no need to actually explain the process), and now you can reproduce this effect yourself!

But how does this let me defend myself?

Well, if you have the understanding and the means to power this phenomenon, then it's not hard to imagine building something able to disrupt this phenomenon as well! After all, your researchers understand this process very well (they're rather enthusiastic about opening a new branch of science), and they've made a number of breakthroughs!

For example, they now know not only how to replicate this process, but also how to disrupt this process! And once they know how to do it, it's only a matter of time before they build something that can do it! They're scientists after all, and one of the fundamental principles of science is verification!

Admittedly, there's no guarantee that this process will be as easy to perform as the original phasing process we observed, so it could be particularly expensive to do so. Still, a little bit of handwaving and this process's resource consumption becomes at least manageable, if not insignificant.

Now if you have the resources to fund the research into this, then you almost certainly have the resources to either patent this technology or otherwise acquire this technology somehow. Even if you don't have those resources (perhaps you are a competitor to the people who did fund this research), there are... other ways to acquire it. But regardless of how it's done, you need that technology if you want to keep yourself safe from people who can phase.

And once you have that technology, all you have to do is deploy it in such a way to keep you and your assets safe from those... phasers?... who would otherwise do you harm! Generate an anti-phasing field around your home! Set up a "honeypot" safe in a sealed room as bait and trap the phaser when they try to break in! Build an anti-phaser into a gun, and briefly activate it whenever it fires a bullet! Doesn't matter! You now have the means to block, trap, and kill a phaser just like you could any other person!

As for how this technology works, what its limitations are, and so on, that's whatever you want it to be. Have fun!

  • $\begingroup$ From the question: "The setting is modern times to near future, with currently no power dampening tech available." $\endgroup$
    – Muuski
    Nov 26, 2019 at 19:52
  • $\begingroup$ @Muuski I took the "no power dampening" to mean that you can't use tech to turn powers off. This is different in that it targets the physical mechanism that a specific power uses. The power is still active and in effect, but physical conditions are introduced to stop that particular process from being effective. Basically, we're introducing conditions that this super power isn't adapted to and cannot work around. Think of it like surrounding a Magneto-type character with a stronger magnetic field than they can produce. Their powers of magnetism are still active, just not effective. $\endgroup$ Nov 26, 2019 at 20:09
  • $\begingroup$ @Muuski The OP stated that there was "currently no power dampening tech available". They never said that it couldn't be created. $\endgroup$
    – overlord
    Nov 26, 2019 at 20:22
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    $\begingroup$ This is more akin to putting something up around the light, or interfering with its emitted lightwaves to keep them from ever reaching your eyes (magical pseudo-science I know, light doesn't work that way, but this is fiction). The light is still turned on, and it's still burning energy - just, the light it emits is never seen or felt, so it looks like it's turned off. $\endgroup$ Nov 26, 2019 at 20:37
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    $\begingroup$ A more accurate analogy - how do you interrupt radio technology? You broadcast on the same frequency. You haven't turned the radio off, you've just made it useless. And if you want no radio communication happening, you broadcast on all frequencies. $\endgroup$ Nov 26, 2019 at 20:39

This being is invisible and invincible.

Taking your first point at face value, this entity can choose to turn its whole body intangible, meaning it will not interact with any of the common types of matter we find here on earth. As long as it remains intangible, it cannot be affected by any kind of wall, gas, or projectile. Because it can turn other objects tangible/intangible at will, there really isn't any reason for the being to turn its own body tangible and make itself vulnerable - it can just wear a pair of gloves which it turns tangible whenever it needs to interact with a physical object.

The being is completely safe so long as it remains intangible, and it has no compelling reason to ever become tangible. There is nothing you can do to stop it.

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    $\begingroup$ It needs to eat, drink and use the toilet. If intangible it can't touch food, therefore, it will need to reform. Personally, I'd target the toilet. More of an immobile target that way $\endgroup$
    – nzaman
    Nov 25, 2019 at 19:10
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    $\begingroup$ @nzaman Interesting point, it's very unclear exactly how eating/drinking would work for this entity. Can they just grab a sandwich, turn it intangible, and swallow it down? Do they need to be tangible to eat/drink? Not sure how much of a liability the toilet is, though, as I don't see a need for it ever use one, or be tangible while doing so. It has no privacy concerns while invisible, and given the fact that it can walk on air, it can pop a squat literally anywhere, making the toilet itself irrelevant. It can take an invisi-poop anywhere it wants without exposing itself. $\endgroup$ Nov 25, 2019 at 19:17
  • $\begingroup$ Yes, and at that point it will be vulnerable. I doubt it can invisi-poop while moving $\endgroup$
    – nzaman
    Nov 25, 2019 at 19:21
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    $\begingroup$ @nzaman As long as it remains incorporeal, it can't be harmed. What am I missing that makes it vulnerable? Even if you know exactly where it is, you still can't touch it unless it chooses to become tangible, which it wouldn't need to do to have an elimination. It could sit on the can singing and reading a book, and you still couldn't do anything to stop it. $\endgroup$ Nov 25, 2019 at 19:51
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    $\begingroup$ This sums up the problems with the OP's premise. As written, intangibility has no limits on duration or capabilities. Thus, there is no reason to make oneself tangible and vulnerable, since you can do everything while intangible. There must be some reason to remain substantially tangible a non-trivial portion of the time, either due to being incapable of certain tasks while intangible or else due to limits on how/how often/how long/etc., that one can be intangible. $\endgroup$
    – Palarran
    Nov 26, 2019 at 1:52

Two words for you: nerve gas.

Best way to prepare an area you're anticipating them entering. By way of a bonus, you can seal it up nicely to reduce the risk to people outside. Initial exposure to a fatal level of neurotoxin can be unnoticable. Even if they just phase a hand in, it can seep through the skin, if you choose the right nerve agents.

By the time they realise their terrible mistake, it will be much, much too late for them.


Considering it can do whatever it wants, whenever it wants, and is not affected by anything it doesn't want to be affected by, there are 2 options:

1.Something very special (and probably unknown) - like cryptonite for Superman, or:

  1. Distance. Distance would be your only defense. You mention that it can "walk", however if we imagine this being having powers similar to those of the Matrix, but a bit better (they seemed to be able to only activate only when their whole body is in the clear, while in your case different parts can operate separately as needed).

This puts the following question:

If the being is in it's invincible mode and no part of it's body interacts with anything, is it still affected by gravity? If yes, then gravity would be one of the options, if no, then that should somehow cover the distance part, considering it is not affected by Earth's gravity, and the Earth is moving through space at huge speed, all you would need to do if somehow force it in it's invincible state for a somewhat prolongued period of time (technically a few seconds would be needed).


Assuming 1) the attacked anticipates the attack and has information about the abilities of the attacker 2) the intangible person is still visible and 3) breathes normal air: I would video-survey the area, being careful not to have walls/floors thick enough to hide within. When I detect the attacker, I simply flood the access routes with gas. I assume the attacker turns tangible when unconscious? If not, do they fall through the floor? If not, well, it might be safer to simply kill them.


Turn off the light

If he can see you he can't attack you. Sometime running is the best outcome, for your next encounter be sure to be the one coming from the shadow. I guess even this godlike being must eat or fall asleep.

SmokeBomb, flashlight, illusion, send him inside a portal to an unknown and unpleasant location.


Make him jump off a train, he will keep the same speed as the previous frame (the train). If he doesn't materialize again he will never stop, cause no force is slowing him down. When it does, he will likely sever extreme damages.


This is in fact a solved problem in the Warhammer 40k universe.

Necron Wraiths perform almost exactly this kind of behaviour in combat to allow their weapons to bypass body-armour and even the victim's skin so they can strike at internal organs.

They have essentially two phasing behaviours. They can phase-attack, where their weapons pass through body-armour and even the skin of their enemy without harm but slash at internal organs and components (of machinery)
They can also use their phasing to defend themselves by completely becoming intangible.
The phasing is very rapid, so they can use it to allow bullets and projectiles to pass through them

They do not have the ability to attack while fully phased, so they have to "decloak" to attack, which renders them vulnerable. Generally it's not a problem because they decloak while lunging for the attack.

Defending against them essentially entails sticking a solid object in their path while they lunge, so when they decloak they impale themselves on it, or are forced to retreat or recloak, stopping their strike.
Alternately, timing your attack to when they're lunging is effective too.

For bonus similarities, Wraiths can fly and see through walls and in complete darkness...

  • $\begingroup$ Weirdly... one of the least scary of the Necrons you can meet.... $\endgroup$
    – Patrice
    Nov 26, 2019 at 16:50

Create a situation where he has to be both tangible and fully intangible

Like avoiding danger while staying on a platform.

(Please feel free to correct my grammar and prepositions without asking)

For example, attract the attacker on a ladder above lava (or anything else lethal), then trigger an explosion on him. He will have to turn fully intangible to avoid the explosion, but he can't do that while staying on the ladder. He'll fall through into the lava. Your rules doesn't say what happens if he falls into lava while being intangible but I don't really see how he could get out alive. And you might not even need lava. Consequently:

Making him fall inside the ground. Falling from a high point might be lethal in all cases, depending on your rules. When he reaches the ground at terminal velocity(*), if he's tangible he'll die instantly, and if he's intangible he'll fall inside the earth (and will keep falling until he decides what to do!).

Then what happens, based on your rules, if he's inside matter and he tries to become tangible? Maybe he just can't, if so he'd keep falling towards the the center of the earth (eventually reaching the other side), but there's no way he can breathe so he'll suffocate in no time. Maybe if he does he dies instantly (or just lose a body part, if it's just a arm in a wall for example). Either way he's dead.

Ultimately it's your choice, but if you want to give the attacker a weak point it's a great choice, it makes sense.

Also, based on the fact that he can "walk" on any surface a normal human can, there's a choice you have to make. I see two possibilities: either he always keeps the sole of his feet tangible, or the ground magically repulses him. If it's the latter, he'd reasonably crush on the ground even when intangible, so I think the former makes more sense. But if he's falling really fast, making a small part of his body tangible won't save him.

(*) As a bonus, if he stays intangible while he falls he'll never reach terminal velocity because the air won't slow him down, so he'll keep gaining speed indefinitely :)

  • $\begingroup$ This being can "walk on air" - who knows what that actually means or what rules it follows, but I'm interpreting that as "can't fall unless it wants to". The being also can't fall inside the earth, as it can "walk on any surface a tangible person could". Even if they did fall through the ground, they'd just have to wait ~45 minutes until they fell all the way through and came out on the other side of the planet, or ~90 minutes to come back to where they started. This is actually a useful way for them to get around, not a dangerous liability. $\endgroup$ Nov 26, 2019 at 14:35
  • $\begingroup$ @NuclearWang Ok, I missed the part about walking on air. That's pretty inconsistent to me (no mass when intangible? How can it even walk?) so I'll leave it for now. But if they can "walk on any surface", when they reach that surface at terminal velocity, what would happen? Would they just lose all their speed instantly without suffering any damage? Being intangible doesn't mean you can break every law of physics. You just don't interact with baryonic matter. $\endgroup$ Nov 26, 2019 at 15:00
  • $\begingroup$ @NuclearWang And if they fall at all, that means they're subject to gravity (or they'd just float around when they're intangible). So as soon as they reach the core they'll be attracted back to it and fall in the other direction until they stabilize inside the core. $\endgroup$ Nov 26, 2019 at 15:00
  • $\begingroup$ When they reach the core, they'll be attracted back to it and start to slow down, but they'll have enough momentum to carry them back to the surface before stopping. With nothing but gravity to slow them down, they'll oscillate from one side of the planet to the other, but there would be nothing to stop them in the core - they're basically a pendulum that never slows down. They are a one-man Gravity Train. I have no clue how the selective interaction of the intangible body with air or normal surfaces is supposed to work, so I'll just leave that be. $\endgroup$ Nov 26, 2019 at 15:32
  • $\begingroup$ @NuclearWang Yeah you're right. I had a conversation about it and as it turns out, because there's no friction you can basically use orbital physics. Then he'd just reach the other side and keep going until he's at the same altitude. Unless there's a mountain on the other side he'd be fine. $\endgroup$ Nov 26, 2019 at 15:46

The attacker can still eat, drink and breathe and has full sensory perception, even if the sensing body parts are intangible.


If your creature can still see, then they can have their eyes damaged by intense light and if their intangible body parts can be affected by light then that means they are constantly vulnerable to lasers.

You might say "Lasers don't cause that much damage" but dying "by a thousand cuts" may be enough to deter any attacker long enough to escape.


Sniper rifle.

Or basically any gun from an ambush.

Let's assume they don't have supernaturally fast reflexes. (If they had, it would be a superpower on its own). Also we assume these beings don't spend all their down time phased.

Most bullets fly faster than sound, so if the shot is fired from outside the target's field of vision, then the bullet will hit before the sound of the gun can be heard. Even if phasing out is an instantaneous action and it doesn't require any preparation or concentration, and the target starts phasing as soon as the bullet is felt, the fastest human reaction time is around 0.12 seconds (most healthy humans average at about 0.25 and it's insanely hard to reduce it below 0.20 even with training)

During that time a rifle caliber bullet (with a muzzle velocity of 850 m/s) can travel about 100 meters, more than 300 feet.

This means that even if the intangible being can instantaneously become intangible as soon as he feels the bullet hitting, and even if he has reaction times a thousand times faster then the fastest human, the bullet already splattered his brain before he can turn himself intangible.


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