I've gotten so into Undertale that I've created my own OC and found a place for her in the game. I made her as none Mary-Sue as possible (though she is slightly mary-sue in Genocide admittedly) but it doesn't really matter what others think. She is mostly for role playing. However, I've had fun with writing out her roll in the games and different phone calls, so I want to post them all. So read at your own risk.
These were posted in parts elsewhere so I made them in parts here.
Umbrieal is a shapeshifter who lives in Snowdin forest along with her father. Unlike most other monsters, she came to the underground many years after the imprisonment. This is because, as shapeshifters, Umbrieal's family was able to blend in with the humans. Some by making themselves look human, and others by turning into animals.
Umbrieal's father was one of the few that made himself look human. This eventually led him to meet June; a human woman who he would later fall in love with. In time that love would be returned and the two would marry with in a few years. Shortly after, Umbrieal was born; making her partially human.
June knew her daughter and husband were shapeshifters, but loved them anyways. When Umbrieal turned 7, some humans saw her use her shapeshifting abilities and got scared. They had heard rumors of monsters stealing souls and tried to kill the girl out of fear. However, June jumped in front of her daughter to defend her and ended up taking a blow that would take her life. Before anything else could be done, Umbrieal's father grabbed his daughter and the two escaped to the underground.
The trauma of seeing her mother sacrifice her life to protect her's from people she thought she could trust caused Umbrieal to lose her voice. Though she could still make noise (laughing, groaning, etc.) she could no longer form words and had to learn sign language to communicate with others.
Umbrieal spent the first couple months in the ruins as her father built a house in Snowdin forest. There she formed a bond with Toriel, who helped the child as much as possible. Mostly by preparing her for the world outside the ruins. For, though Umbrieal had been told of monsters and how they were kinder than humans portrayed them as, she had never met one before; outside Toriel herself. Toriel also helped the father teach the girl sign language and gave them the room all former fallen humans had used before they left.
Umbrieal is uneasy and uncomfortable living in Snowdin for the first couple years. While she isn't necessarily scared of any of the monsters, she'd rather stay home where she won't be seen or have to interact. When she has to go to the town, she'll often make herself look like one of the animal monsters or change her appearance so she won't appear human. She hates going into town, however, and won't do so alone until she is around twelve years old.
Now, because Umbrieal had a human mother rather than a shapeshifter, her natural abilities are weaker. She can not change her gender, maker herself look exactly like someone else or increase her height. However, she can change small parts of her body at a time, such as giving herself gills or wings, or a tail. In relation, she can still change her appearance, such as changing her hair or eye color. However, she can not change into two different things at once, unless there is a creature like that. If she tries, it will give her a splitting headache.
Also, being half human gives her a partial human soul rather than a gray monster soul. Hers is light yellow which is later revealed to represent forgiveness. Despite feeling betrayed by the humans that killed her mother, and tried to kill her, she forgives them for what they did. Though she is still hurt, Umbrieal understands that fear can make people do horrible things. Regardless, she and her father keep this fact secret as they fear her soul may be stolen to use for the barrier; though it is unknown if that is even possible.
Umbrieal is a preferred pacifist. Meaning that for the most part she is peaceful and doesn't like to fight. If she is forced to fight she'll either use defensive magic or dodge and try to run away. She does this by trying to only disarm the other monster or pin them down. She'll never try to badly hurt or kill the other monster. If she greatly hurts them, she'll feel horrible about it.
Lastly, it is actually unknown if Shapeshifters are actual 'monsters' or not. Their original form is unknown since they are born looking like whatever form their mother takes while pregnant. Most shapeshifters call this their "default" form. It is unknown what Umbrieal's father's "default" form is, but Umbrieal's is human. Another indication that they are different from all other monsters is that, when they die, their bodies do not turn into dust, but are instead encased in stone. Since Umbrieal is partly human, she is unsure if this is what will happen to her when she dies.
Powers
Aside from her natural shapeshifting abilities, Umbrieal is able to use magic. Unlike many, her magic takes on a light yellow color; the same as her soul. She uses this magic mostly for defense but has two weapon forms. One is a chain and other are large staples. Though they are weapons, she uses them for defense only; either by disarming or containing the one attacking her. She is also able to create bubbles/shields and platforms with this magic.
Another power Umbrieal has is speed. She is incredibly fast when she wants to be. Not even she really knows where this comes from, though. She's not even sure if it is a actual power or a natural ability of hers'. Regardless, Umbrieal only uses this speed when she really needs to, as it easily tires her out.
Relationships
Outside her father and her OC boyfriend, the only real relationship Umbrieal has is with Papyrus and Sans. This is because they became her babysitters a few weeks after she started living in Snowdin forest. Her father knew he'd have to collect gold so he and Umbrieal could buy food and other things when needed. However, he also knew he couldn't leave her alone for long periods of time. So he set out to find babysitters to watch his daughter. Papyrus, who saw it as some kind of royal guard training, agreed and more or less convinced his brother to help him.
At first Umbrieal didn't like the skeleton brothers and would try to hide in her room when they came over. They were the first monsters she'd seen since Toriel in the ruins and she didn't know if she could trust them. When she eventually became comfortable around the two, she became closest to Sans. Papyrus's level of friendliness and enthusiasm made her slightly uncomfortable but she still cared deeply about him. After a couple years Umbrieal got so comfortable around the two that she accidently called Sans 'uncle' while talking to him. It is something he has teased her about even in the present time. Regardless, she continues to call him this from time to time, though in a playful way, and has also taken to calling Papyrus 'uncle' every now and then.
