Cobalt

***SPOILER WARNING*** (UNDERTALE)
The storyline involved with the following non-canon character directly revolves around information and characters very deep inside the game of Undertale. This character page  guarantees game spoilers  if you have never played the game, or have only explored a few aspects of it so far.

Name: ???
The girl has adopted the name Cobalt in an attempt to protect herself. Even those closest to her are unsure what her real name is... or was... or if they even knew her.

Origin: The Underground
Cobalt had awoken beyond the Barrier, deep inside the Underground and laying in a bed of Snow. The woods surrounding the path lead her to a small town at the mountain peak called "Snowdin". She saw her first Monster at a distance killed at the hands of a child. When she witnessed another mourn the loss and drop a scarf from his pocket, she attempted to return it. After a near death experience running in to the dangerous child responsible for the apparent genocide of the Monsters along the way, she ran for her life and fell in to a battle between the child and the earlier seen Monster she was trying to catch up with. Getting caught up in the mess she saved the Monster from the child, but became targetted herself for being Human in his blind rage... and her life ended.

Her desire to do something about what she had witnessed gave her determination, and she discovered her ability to reset. Moving much more quickly this time she managed to meet the skeleton who killed her and blindly warned him about the inevitable danger that was about to befall his brother if he failed to get back to Snowdin in time. With many questions for her later, he left immediately and managed to stop the child from defeating him... This was the beginning of a large altering attempt of the timeline.

Various events brought her closer to being friends with Sans, even living under the same roof as him and his brother. Eventually she even befriended Papyrus, and only then did her abilities of seeing in to the future begin to show. Ultimately she learned how to save the Underground and free them all from the Barrier, but it would be at the cost of destroying herself. She couldn't exist in that timeline, and Sans wouldn't allow for it.

Against his wishes, she followed the slim lead on another who had successfully removed their existence even if by mistake. She traveled to the Core and threw herself in to it, and with that she was forgotten, but not before using what Determination she had left to alter the timeline and throw everyone before her arrival back to the day a child named Frisk fell in to the Underground... The pieces had been set with Sans retaining slight memories of her visions. Placing him at the right place at the right time, he could guide Frisk on her journey to becoming a True Pacifist.

So why is Cobalt alive now? Where has she been, and how did she return?

Allies

 * Sans


 * Papyrus

Abilities

 * Save: In the Underground, her Determination to live slowly evolved in to Determination to Save the Monsters, specifically by Saving the Prince. In the past, her Determination was greater than that of Flowey and a Chara-guided Frisk. Currently, she faces very little opposition in the Underground as most Humans and Monsters have LEFT the Underground. When deeply inspired and filled with Determination from a setting or experience, she can later return to that point in time... even after Death.
 * Reset: Similar to her save ability, she can Reset the timeline of the Underground to return to where it all began for her upon arriving into the Underground. Everything, including her own saves, is re-written to that starting point as long as her Determination out-weighs others.
 * Determination: Being a Human, she is capable of becoming Determined. That Determination can outweigh others in the Underground and grant her manipulative powers against the flow of time. She can only cause time to unnaturally return to the past, and her state returns to that of the time revisted. She cannot willingly (or unwillingly) move forward in time at any greater rate.
 * Composing Psychic: What truly made her stand out as a Human in the Underworld was her strange ability to recall important scenes from other timelines in the Underground through composing music (themes from the game itself used during key times/battles). The visions her finished pieces gave her are able to be shared with those close around her who connect with her emotionally. It was this very ability that alerted Sans to the Grand Finale that the Prince was still alive, and that Frisk would be the destined child to free the Monsters from their prison... but at what cost?
 * Gaster Blaster?: This is an odd one... and likely has something to do with a trick up Sans' sleeve, or an encounter with ... huh... what was their name again? What was I talking about?