11: Robecca Steam:
I have some reserves about classing Hexacia Steam's creation as a monster. She was, after all, created by human hands. Then again, so was Victor Frankenstein's monster. But, I suppose that is a discussion for another time. For all intensive purposes, I am going to be including her here as she does attend the school.
Robecca primarily outranks the other two for one simple reason: She is an automation made from copper. This renders her immune to physical pain, illnesses, and poisons as well as many of the powers other monsters on this list have. Unfortunately, while her abilities are impressive (she is Hexicia's handiwork after all), they do not outway the other monsters unnatural skills.
Steam can be a very dangerous weapon. It can cause worse burns than fire. Water must reach 100 in order to boil into steam. That means steam is at 100 minimum, and can reach temperatures much higher. Although, it could be argued that steam burns worse that fire because people are more cautious with fire than they are with steam. I wouldn't know; some people are smart, others are idiots. As it is, steam, being a form of gas, dispersis and cools rapidly. This being, Robecca would have to be in very close proximity in order to weaponize her steam. If she has enough, it could be used like a smokescreen for a getaway or attack. Of course, any draft would undo the fog. I really shouldn't have to, but I will be including the final steam related perk this girl has just in case. Steam is a form of water. Water can put out fire. Onward.
The girl is well versed in the art of rocket boots, providing her with breakneck speeds and essentially making her a living (sort of) copper bullet. She is very agile and reacts quickly on the track. I'm not sure how she would pitch if put up against another monster in a fight, but I suspect she'd have a solid chance. She is also very daring, or a dare-devil as the kids call it these days. Could make for some inconvenient situations.
Unlike Frankie Stein, Robecca Steam is not as heavily dependent on an external power source. She may need a charge every month or so and perhaps some fresh cole every other day. Seeing as water is a readily available resource and also needed by every other monster, I do not think it counts as a form of limitation.
All in all she appears to be a well rounded creature. Not vulnerable, but not particularly threatening neither. Her scatteredness and habit of arriving late could pan out for or against her, so I see no reason of putting a fuss about it.