I'm writing a story where my lead character has two forms and he swaps between them frequently. I'd like to know the advantages and disadvantages of various kinds of triggers for the transformation.

Possible ideas:

  • Time of day (every x hours)
  • Emotional state (transforms when he gets angry)
  • Verbal (some "magic word")
  • Special scientific device

I'd like to know if these different triggers (or others you can think of) have influences on story elements; like the plot or characterization or character psychology. In other words, what should I consider when choosing one over the others?

  • Hi Josh, and welcome to Writers. Stack Exchange is not like other sites. We are a Q&A site, not a discussion or brainstorming board. Questions need to be concrete and answerable with the potential to help others in the future. This is right on the edge of "what to write" (meaning "help me write my specific story") which is off-topic for us. Sep 22, 2019 at 13:29
  • If you can edit your question to reflect something like "If I am writing a story about X [redemption arc, hero's journey, space opera], which one of these methods would work better?" it might work. Right now any of these transformation triggers are viable; it would depend on what kind of story you're telling and how this method could be a help or hindrance or how the character could use it or overcome it. Sep 22, 2019 at 13:30
  • 3
    I changed your question to make it less of a "what to write" question (which is prohibited here) and more about the craft of writing (which is allowed).
    – Amadeus
    Sep 22, 2019 at 14:27
  • 2
    Are the "two forms" a sort of Yin and Yang, Jekyll and Hyde situation?
    – user34214
    Sep 22, 2019 at 16:45
  • Welcome to Writing.SE Josh, glad you found us. We have a tour and help center you might wish to check out.
    – Cyn
    Sep 23, 2019 at 14:49

3 Answers 3


A method like time of day is very constricting, and becomes more like a disability than an advantage. Consider werewolves that convert, like it or not, on the full moon. It has been used as a story advantage when the werewolf feels compelled to lock themselves up for the full moon, or usually does and cannot get there in time, etc. But the scope of the story is still very limited.

Emotional state is similarly constricted; Bruce Banner becomes the Hulk when he gets angry. We get tired of it; or at least I did. The episodes become formulaic, there are only so many trigger points, and in a way you know Bruce is never in any real danger, as soon as he gets hurt here comes the near-immortal Hulk to the rescue, and all it really costs Bruce is a wardrobe expense, embarrassment, and moving on to his next angry episode.

A method of choice is the most flexible option, and perhaps too flexible, because it becomes like a magic wand in the hands of an expert wizard: The solution is always there. If a physical object (device or potion or amulet or whatever) is necessary for the transformation, then depriving the character of the physical object can be a useful plot twist.

Another way of restricting a transformation of choice is to use a special reserve of some sort, magical or not. The transformation potion requires the golden nectar, if the supply is out, it's out. Or the transformation is physically brutal and exhausting, try it twice within 24 hours and bleeding lesions appear on the skin, try it three times and you may rupture organs and die. Then you can engineer the plot so this is exactly what has to happen. We see the hero in an emergency do a second transformation with the expected consequences, to prove they are real. Then later the hero has to risk a third transformation to save his mission, and we know he is risking his life for his values.

What you need to do is balance these opposing forces; you don't want his skill too easy to whip out, and you don't want it too hard to use when your plot line calls for it. In other words, you want the plot to flow naturally and not have to force it to fit specific times or conditions, and you also want the use of the skill to be relatively rare so the reader is looking forward to the next installment of its use. That won't happen if the skill is on display two or three times per chapter.

  • One of the nice things they did with Hulk in MCU (at the start, at least, and again towards the end - it was slightly more 'traditional' in the middle) was making the switch between Banner and Hulk relatively easy physically, but not mentally - neither of them wanted to cede control to the other, but they could do so quickly when needed or unavoidable. ("That's my secret, Captain: I'm always angry.") Of course, that all gets flipped around during Infinity War... The story then becomes less about "preventing the change", but accepting that sometimes you need "the other guy"'s help. Sep 23, 2019 at 8:02

Exact mechanics are less important than control

No matter how the exact transformation works the key thing that matters is how it is controlled. A scientific device, a superpower, and a magic wand, all fundamentally work the way just in different settings. You really need to choose between the following three styles of ability:

  • At will. The character is in control of their transformation. They can switch back and forth whenever and wherever they choose. The character can use their alternative forms strategically and plan to make the most of the abilities of each form. This makes the character stronger and capable of achieving things neither form could alone.
  • Forced. Werewolves at full moon, Fiona from Shrek, characters with specific triggers (often based on the moon or time of day) that force them to change, usually against their will. These type of transformations are more often described as a curse than a blessing. Stories involve characters learning to deal with their curse and overcome it, succeeding despite their curse rather than because of their superpower.
  • Emotional. The Hulk is the ultimate example here. These characters transform based on how they feel in a given moment. It is difficult to predict when the will transform and harder still to control when they do. The common trope is that these characters learn to control their emotions and transition to at will transformations.
  • Something else. These are just a few examples of how a transformation ability works, you can likely imagine any number of other complicated triggers. Ultimately it comes down to how the character can control/understand their ability to transform.

Another important thing to consider is how the character view their transformation. Is it a blessing? A curse? Do they despise their other form or view it as their secret weapon? Would they give up the ability if they could? These feelings with inform your character development and the narrative you tell from it.


@Amadeus mentions constraints. Constraints are like the walls of a house - they are limits, but also supports of the structure. The constraints define the shape of the story you tell.

If change is forced on the character by some outside circumstance, such as time, your story must perforce deal with the inconvenience of having to transform whether one wants to or not, as well as, perhaps, being unable to transform when it would have been convenient.

If transformation is always available to the character, one can examine the price of transforming - whether physiological (as @Amadeus suggests), social, or perhaps mental. (For instance, if the character spends too much time in the other shape, they might struggle to transform back.)

There is also what the character transforms to: becoming The Hulk would be different from becoming a moth. The latter can solve interesting plot problems, but it is also vulnerable to being squashed and to flying into a flame. The Hulk is vulnerable to nothing much.

In effect, there are three elements you want to balance: the transformation's capacity to solve problems, the ease of transformation, and the downsides of transforming. If transforming is easy, and its capacity to solve problems is high - the downsides must be serious. If there are few downsides then either the transformation creates more problems than it solves (think of the traditional werewolves), or else the price is high. The particular trigger would be derived from this consideration.

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