In a training scene Ella explains that that is not the case, you have to exert your power to maintain changes. Which either means that at lvl 5 that rule does not apply to her, that WW just forgot about it, or that she is still alive.
I'm aware of that piece of dialogue. However to me it seems that "maintaining" means "fixing" in this context. When MC talks about his transformations, the common theme is the energy expended when healing or while transforming.
I think the most important piece of dialogue that explains how this works is the following:
On Healing Factor
You "And finally my healing factor, an extension of my transforming ability."
You "My body wants to be in its natural state, the state I'm in now. Any injuries I sustain tend to mend themselves as my body shifts back into its default state."
You "Arguably the best part about this whole thing and the only reason I'm still alive. "
You "The only drawback I've noticed is that since my body wants to return me to its default form when I'm injured, if I'm using a full body transformation at the time of receiving my injury I lose it if I let my body heal itself."
You "I need to specifically direct the healing myself if I want to maintain my current transformation, which takes a lot more concentration and effort."
These few next quotes is everything I can find related to energy expenditure when the MC uses his ability:
On 3rd evolution's plate armor:
You "It's also more difficult to shapeshift with it on. Adding more material on top of my body just means I have to waste more time and power to alter it when I'm changing forms."
When reviewing his forms after Klaus fight:
You "Now for the transformation that made my zoo trip so successful. The wonderous fly!"
You "Excellent for travelling unnoticed. However, it is by far the most time consuming transformation I possess. Squeezing all that mass into that tiny body takes a lot of time, as does the reverse when I'm returning to normal."
You "Phew. And I think that's everything. What a workout, manifesting all those different transformations. Good stuff."
You "First... there's my tail."
You "My spine serves as the core for this one, it's exceptionally powerful. At least compared to my normal tentacles."
You "It also seems to act somewhat... autonomously, at least sometimes. I haven't really figured out how it works yet, I'll need some in depth practice with it."
You "But I can change its shape more easily than I can for my normal tentacles too."
scene handtransform2 with dissolve
You "Next, and sort of related. Metal."
You "I have enough power to create it at will now. Although... it still seems somewhat taxing."
You "It wasn't like this in the Klaus fight. I was able to make it so efficiently then, using barely any power. How?"
You "I was acting mostly on instinct at the time, but I can tell when I try to form it now. I can do it, but it's costing me more than it should be. Much more."
train44 dialogue
"Power swells at the base of my spine, flesh as well."
"I can feel each new vertebrae form as my spine grows, vertebrae not made of bone, but rather of steel."
"It costs precious little power for me to create, which is strange, as metal is ordinarily quite costly."
"And yet this tail, it requires barely any effort or concentration to create, almost like it's building itself."
train48 dialogue (this isn't as explicit as the others, but it still mentions that healing is the problem)
You "Although, I suppose I also have my giant form."
You "Easily the riskiest option. Growing that large would make me a huge target, alerting pretty much everyone in the vicinity to my location. My weight also increases more than my strength, so I'm slower, making me even easier to hit."
You "On top of that, the cost in power is high and would increase manifold with every injury I sustain. I don't have enough power to heal more than a couple bad wounds for a body that huge."
train51 dialogue
You "I've trained a lot over the past six months, since I got these powers. More than I ever did as a human."
You "So many transformations learned."
You "So many nights training to increase how much I can transform, how many tentacles I can make, how much flesh I can produce without exhausting myself."
As you can see, there is a distinct lack of talk about "maintaining" the transformation in a context other than regeneration.
So the MC has to "maintain" control of the healing factor during the transformation when he gets injured, otherwise he will return to his default state which leaves him vulnerable. This is also why he doesn't want to use big transformations. Because both avoiding damage and having to heal less flesh is way cheaper than losing a chunk of flesh and healing it.
The language is pretty consistent. Everytime he talks about maintaining during his training sessions, he talks about regenerating.
Even when he turns into liquid, all talk is about mental concentration, not power expenditure.
"My forearm melts, transforming into a dark, flowing, viscous material."
"I can still control it to an extent, stretching it out and whipping around, but...."
play sound "audio/splash.mp3"
show bmc noarm with hpunch
You "Argh, shit!!"
"I lose it. My control over the liquid breaking the moment I let my concentration slip, my entire forearm dropping to the floor with a splash, quickly evaporating into nothing."
You "Fuck! There goes my arm."
show bmc n with dissolve
"It grows back of course, at the cost of a good amount of power. But I'm suddenly very aware of why I've been so instinctively wary of this ability."
You "I could lose my entire body if I'm not careful... It could all disappear in an instant. The amount of focus I need..."
You "And then, what happens if I turn my entire body to liquid, my brain included? How can I focus without a brain? How did I do it against Klaus?"
You "I was weaker then than I am now but... the focus I had was something else, almost like a trance."
At this point I just take for granded that all energy expenditure happens either when transforming or when regenerating and there is no such thing as energy expenditure to maintain the form's state and that's what Ella was taking about too.
