Numa

She is very indifferent, doesn't talk too much. She's cold hearted to most and will slowly bring them down, as her instinct as monster tells her to. She does have pity for young children or very helpless individuals and lets them go unscathed. There's one person she takes care of, however not, because of feelings towards them, rather because she perceives it as her duty.

Numa was born as most monsters in Elsekai as a manifestation of the nature around her. She became sort of a personification of the swamp.
When Numa was born, she did not have such a clear form. In fact, it's questionable to call her by a name at all. She was a monster, reigning the swamp. She would pull in travellers, make them drown in the depths of her territory, so they would not disturb life in the swamp. She'd make sure that the plants would flourish and that the landscape would be a good home to the animals living within it.
Numa did not have the capability to think at this point in time. She was merely a monster acting on instinct.

However, this changed, when one of the animals in her Swamp died. Well... it didn't die. That was the problem. Instead of dying, it sucked in the natural energy around it and started changing its form. It became... humanoid. Numa was confused for the first time in her life. This was not something she could solve by instinct alone. On the one hand this was an animal she needed to protect, on the other hand this being certainly looked like a human, she should kill. For the first time she had to think, in order to make a desicion. And she decided to protect this being, this person. After all, that was her duty, right?

Over the years the person started helping Numa. He helped her with the travellers, either leading them out of the swamp safely or leading them into it. He started learning speech by listening to them. And he learned fast. Soon he could talk. And Numa learned speech from him. He started enjoying to talk to travellers. To find out about the world outside the swamp, to get to know people and their motivation. He started leading people out of the swamp, Numa would've killed. And Numa let him be, because it was her duty to take care of the swamp and he was part of it.
Over the years, Numa became increasingly humanoid herself. Maybe she became softer too. If so she wouldn't show it tho. At the same time her companion started showing more and more interest in the world around them. And one day, a person came by looking for shelter for himself and his group. And he decided to provide that shelter within the swamp. Numa decided not to go against him and instead helped him building a home for the travellers.

Thus the swamp became the base of a group of rebels intending to overthrow the government of Elsekai. Numa herself doesn't really get involved much, instead she's observing whatever is happening.