Hello and thanks for taking the time to read this. I am working on a novel in which a large array of characters will undergo massive transformations, however I'm not satisfied with letting it be simply "Magic" I want the characters to absorb matter or energy from their environments to be able to do so and to have the appropriate amount of damage be afflicted to the surroundings. This is beyond what I really need to do but I'd love to do it as accurately as possible. My question ultimately is: What fields do I need to look into in order to know how to calculate this? I have two ways I may go about this #1: Grabbing the materials raw from their surroundings as whatever it is and using it as makeshift organic matter (For example use concrete to try and simulate the growth of an arm) #2: Converting the matter around them into energy and converting it back into whatever it needs. The second way would be ideal in my opinion though I have a feeling I'm misunderstanding the concept that mass and energy are interchangeable. Either way I'm not asking for you to give me all the resources (though that'd be great!) but rather to guide my studies towards what specific fields I'll need or what specific knowledges I'll need beyond the mass per volume of the common materials in urban construction (the term of which escapes me since my education was in French) As this may help: While I'm eager to learn I'm a highschool drop out so I'm afraid I'm that far behind with random knowledge scattered all over. Thanks to anyone willing to give me a hand with this project and guide my research! Have a good day!