Sans has a very deep backstory as a character in Solartale. After the 3rd Human died, Sans had a run-in with a member of the Royal Guard. Not much is known about this encounter, but it resulted in one fourth of Sans' skull being cut off as well as his right arm. Sans was nearly dead, but Dr. Alphys, who had a thing with playing around with people's lives at the time, was able to put a robotic fourth of a skull on Sans, as well as the "Ultimate Equalizer" As called by Sans, Hyper-Nova, an Sword/Laser arm cannon thing similar in appearence to Mettaton NEO's blaster. However, Papyrus was never seen after the incident and was belived dead. Sans procceeded to be looked up to as the ultimate killing machine, often taking on jobs to kill any criminal.
Sans in Solartale is very similar in appearence to his Vanilla Sans counterpart. The most noticable difference is his right arm is missing, but has been replaced with Hyper-Nova. His top-left (Top-Right if your looking at him from the front) quarter of his skull is also robotic.
In battle, Sans is merciless, being able to kill in one shot with the Hyper-Nova. If somehow after that his enemy is still standing, his assortment of bones and Nova Blasts will surely end anyone's life very quickly.
2 hidden Sans fights can be unlocked if the player does 3 Genocide Runs in a row. Sans recalls resets, so he remembers the player killing him three times. After the player reaches Snowdin after 3 Genocide Runs in a row, Sans will quickly walk behind the player and proceed to enter a fight with him. If the Player is not on their 4th Genocide Route, the fight can be easily skipped by simply going into the act menu and selecting the talk command. However, if the player proceeds to kill Flowey (Who in the Solartale universe is Sans' adoptive brother) This "Enraged Sans" fight will start again, this time, however, Sans will annihilate the Battle Menu. After that, the player will have to survive Sans' Attacks for 30 turns before the FIGHT button regenerates and then Sans is one shot killed, similarly to his Original Undertale Death. ASGORE will replace Sans in the judgement hall, but Sans will be standing in front of the throne and unveil that he has stolen the six souls, but also somehow obtained a seventh soul, similar to Papyrus. This starts the longest fight in the game. The fight is described by the owner of Solartale as "A pure spectacle" and it truly is. The bullets constantly change color, and there are several of them, giving the fight a Touhou feel. In phase 1, Sans will go down after 4 hits, but then the infamous line "But it refused" appears and then the fight goes to Phase 2, AKA the Light Blue Soul Phase, this lasts 10 minutes, and you have to survive 10 attacks for 10 minutes, then, the Light Blue soul will tire out, and it then jumps to the Purple Soul Phase. The fight then circles through the other souls, With the same tiring time of The Light Blue Soul, making the fight over an hour long. After the Red Soul's phase, Sans will collapse. The souls have been drained, and he then talks about how he never saw his younger brother (Papyrus) After his arm was chopped off. The player then is given the choice to Spare or Kill Sans. If Sans is spared, The player will shatter the barrier, Followed by The Player and Sans leaving the Outer World, followed by a very grim ending. At a night on earth, A cutscene will be shown of the player murdering Sans in his sleep, followed by a Chara Jumpscare. If the Player kills Sans, They will be approached by Chara, who then does the same thing as they do in a base game Pacifist Ending.
Sans in Solartale's Personality is a mix between His original and Undyne's Personalities. He does not hesitiate to kill, but he will not outright kill a human like Undyne. He is also very nice, but at the same time, he can be very angry and kill you out of nowhere.
This Sans is the one of the most powerful in the multiverse. He has all the abilities of Regular Sans except Gaster Blasters, But he also can mimick anyone to trick a player. This power is displayed quite well while in battle with him, mimicking Mettaton in his base form very easily. His Hyper-Nova is equipped with a sword that according to the creator of Solartale, can cut through Error!Sans' Strings, which since Error is a glitch, are technically the hardest thing in the Undertale Multiverse, with ease. He is also extremely mobile, letting him easily keep up with characters like other Sans', he has gone into The Void and Anti-Void and survived, and has even killed certain variations of W.D. Gaster.
In his god form, Sans gains power similar to Omega/Paint.net Papyrus, but much stronger. He also gains 2 new abilities:
SOUL Rampage - For this ability, Sans calls on the power of all the souls he possesses and exerts it in an incredible blast of attacks. The 7 Human Souls he has acquired all work together to blast any foe with their respective attacks (EX: A Revolver for the yellow SOUL.)
Omeganova - This makes Sans absorb the energy of all surrounding Celestial Objects and shoot it out in a blast that can destroy over 700,000,000,000 galaxies in a single second.
He also becomes extremely durable, in fact, he can survive being engulfed in UY Scuti's supernova for it's full duration.
- Sans was the first Solartale AU character to be made.
- A game showing what Sans' god battle would be like is currently in development, by none other than I AM INSANITY himself.
- Sans' old design oddly has the same white-to-blue fade as many characters like Asgore and Napstablook.
- According to Insanity, the reason sans is a cyborg is because he factored in technology benifits, since the Solartale System was previously inhabited.