Somehow you managed to knock out an elemental shape-shifter. Where do you put it?
Elemental shape-shifter: A person who can change their body to the four classical elements: Earth (like the material), Fire (think Johnny Storm), Water and Air.
Assume that you are a multi-billionaire, and that you have access to any tech up to our current level.
Assume that you may have to visit the shape-shifter from time to time.
More info: the shape shifter requires magical energy to shift and stay shifted form, if out of magical energy the shift we return to human form to recharge or if unable it will go into hybridization until it can return to human form or gain enough magical energy to remain mobile in shifted form. magical energey is spirtual in nature and nothing you can do to directly block her access to it even send her into the vacuum of space wouldn't do it.
More info fire is the most powerful of the shape shifters form. It can generate theoretically generate the more magical energy. fire form requires the most amount of magical energy and the more hotter it gets the more energy she uses. She also can only recharge a very limited amount of energy outside of human form. So unless you imprision her right next to a magical super battery she is not going to go supper nova any time soon none the less you should probably make sure your prison is can withstand extreme temperatures, but should not have worry about her produce an more heat than a large forest fire.
Water: staying in water form require the second most amount of magical energy. in water form she can dissembled her body and control it's disassembled parts. however she can not control any water that did not originate from her and she requires all of her disassembled parts to rejoin before she can.
Air: less energy then water same rules apply
earth/rock. use a very low amount of magical energy she could easily stay in this form for days with out having to recharge.
She dose require food and drink while in human form. you also may have some questions for her to answer