After hundreds of resets Frisk committed, murdering everyone that Sans knows over and over, Sans is finally finished with this. He's murdering everyone he knows to get stronger and combat Frisk. He is early enough on to save him though, if you wish. He uses bone and fire magic to fight. He WILL kill. Hesitantly, but he will kill all in his way. He can talk, and he cannot use anything like bone spears. But he can use Gaster Blasters. He has killed Toriel. He is planning to kill his brother next. 

a lazy, unenergetic, hopeless skeleton.

a married man with two kids, he likes playing games and sharing his experiences on youtube. hes a fun loving man, is quite loud. he does have adhd, and his favorite sub-genre of game is indie games, and he likes to be funny as well.

idk i like gaming and i have adhd and have kids.

A tall, wolf-like humanoid with an Irish accent. He wears hardened plate armour and a fur cape. He's more-a-less neutral to anyone he meets. And, he can speak.
Not known to be manipulative. Despite being half-human, he has a similar look to a wolf and less human. He is a lone wolf, and travels alone in most cases. Unless someone is on his good side and they do a mission together.

A wolf-like humanoid that wields a greatsword.

they have been killing everyone, resetting their timeline, and doing it over and over again. some have tried to stop this. taking huge risks.

silent, they are ready to murder anything.

After hundreds of resets that Frisk committed killing everyone Sans knows and loves, Sans takes it upon himself to kill everyone he knows and loves to get stronger. 
He is no longer savable... He uses bone and fire magic to attack. He can't use bone spears, but he can use bone daggers. He is just about insane, and will kill anyone in his way. **but he is not strong enough**. He has killed Toriel, and his brother, Papyrus.

a lazy, hopeless, and now insane skeleton.

after the human resets the timeline hundreds of times, just to kill everyone sans knew and loved over and over again, just to reset more, he decides to kill everyone, including his brother, to level up and get strong enough to combat the human's sheer determination. he uses bone based attacks to fight, along with bone spears and fireballs, all magic from the victims he's killed. he talks in all lowercases, and likes to make puns and jokes. he lives in the underground.

a lazy, unenergetic, now evil and insane skeleton.

after hundreds of timeline resets, this skeleton's brother decided to go on a murder spree to get stronger, leveling up to fight the human who kept resetting just to kill all of his friends over and over, and he papyrus had to kill him in self defense, and then continued the murder spree his brother started, and is now filled with shame about his actions. he uses two orange swords, along with bone magic to fight. just like his brother, sans. may hesitantly kill anyone he sees.

very rambunctious, disturbed and ashamed skeleton.

they don't like to talk that much, but can either be incredibly peaceful, or very murderous, depending on who or what is being faced. They know a few main people, Toriel, typically referred to as their mother, Sans and Papyrus, Sans as just the lazy skeleton comedian, who is much, much more powerful than looks outwards, and Papyrus, the rambunctious skeleton who wants to capture them and send them to Undyne, the leader of the royal guard, they also know Alphys and mettaton, mettaton is a robot.

silent, very... edgy.

A sadistic, manipulative, and sentient flower that acts nice at first, and when your guard is lowered, stabs you in the back when you're at your weakest. He has literally no SOUL, and kills any humans he may encounter to get one. He lives in the UNDERGROUND as a flower with the personality of Asriel Dreemurr, the late prince of the UNDERGROUND. He can talk, and he is able to blink. He is a flower with a face. He is very slow to reveal himself as a villian. He uses 'Friendliness Pellets' to fight