So, in my previous question I mentioned a human-like race of polymorphs/shapeshifters from biopunkish world of Gaea. Their "normal" appearance (or Huntress' in particular) is not that different from normal human (medium build, darkish skin, about 1,65 m (~5 ft 5 in) tall, short coarse hair, blue eyes)... except for her body mass which is whopping 320 kg (~705,5 lb). Shapeshifting is her trump card in any battle - it's quite disturbing for an enemy when relatively small girl in mere seconds becomes a 3+ meter (~10 feet) tall beast with giant claws and nigh impenetrable scales/fur/whatever situation calls for.

Hence the question: how can I explain this tightly packed body mass?

In case you need any more reference: think Alex Mercer from first [Prototype] game with high "critical mass" level - same body size, way higher than normal body mass.

  • $\begingroup$ As far as I remember the protagonist/game you mention in the last paragraph, the mass comes from the surroundings whenever he transforms $\endgroup$
    – dot_Sp0T
    Dec 19, 2016 at 10:01
  • $\begingroup$ A really heavy lump of some kind of dense organic tissue? Maybe across the rib cage to protect the heart. $\endgroup$ Dec 19, 2016 at 10:01
  • $\begingroup$ @dot_Sp0T I mean that blue bar you need to fill by consuming biomass for ultimate moves like tentacle explosion. $\endgroup$ Dec 19, 2016 at 10:03

2 Answers 2


Here are a few ideas I had:

Converting Dense Elements to Lighter Elements

You could have her physiology be made of very dense elements (like gold, lead, uranium, etc.) while in her human (compact form), but when she shapeshifts, her elements split apart to form less dense elements (like those in a normal human body).

Compressing and Decompressing Light Elements

One other possibility could be that instead of the elements of her body being elements with greater atomic weight (or mass, I'm not sure which one) and then transforming into lighter elements, you could just say that she has 320kg of normal elements found in humans, but they are highly compressed via some force she controls.

Constant Pool of 320kg Worth of Pure Mass

You could even perhaps have her physiology not be comprised of atoms like we think of them, but as a pool of energy/mass that stays at a constant weight (320kg) held in human form that can shapeshift at will into any form.

Converting Field Energy to Matter and Back Again

Or, you could have the shapeshifter be able to transform the unbounded energy of the four fundamental fields directly into mass at will. That way, her weight when she is in human form would be that of a normal 5'5" female, and when she turns the field energy into a larger form, she solidifies 320kg worth. Like in E=mc2, she would be essentially be taking E from the fields around her and converting it to m and then back again at will.

  • $\begingroup$ You could end up with some seriously weird effects using your last suggestion. $\endgroup$
    – Joe Bloggs
    Dec 19, 2016 at 11:23
  • 1
    $\begingroup$ While these are interesting ideas I'm afraid operating fusion and fission constantly will release enough energy to kill her many times over; to create matter from energy she would need to drain so much of her environment she'd freeze. $\endgroup$
    – Zxyrra
    Dec 19, 2016 at 12:33
  • 1
    $\begingroup$ Handwavium is definitely needed, at least 500mcg per 1000 words of plot, lest the aforementioned side-effects occur! If problems persist, apply handwavium at maximum allowable RDA. :) $\endgroup$ Dec 19, 2016 at 12:38

Use mass from the environment

You can have your shape-shifter take any required mass from the surrounding environment and build this into your plot. If you write in some kind of restrictions (you can't use water as a source of mass), then you have some plot enabling shackles for the shape-shifter to puzzle her way out of.

Obviously, upon changing back to normal size, that extra mass will need to be excreted somehow.

Changing shape downwards (smaller) also requires losing mass, so this could inject a little jeopardy into the plot (she'll need to gain that mass from somewhere to restore full shape).

For simplicity, there can be a buffer range of mass-change that doesn't require taking/adding mass from the environment at all.

Either way, growing or shrinking by a significant amount will require some extra work.


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