Sans is the main antagonist of the UnderRuin AU and the older brother of Papyrus. He has a very similar appearance to Sans of Undertale. He cares deeply for papyrus, but can also be very pushy and impatient with him. when angered or upset, he may have instances where he hurts him badly, but always regrets it and breaks down afterword, promising to never hurt him. some notable differences in his appearance is that he has black bones, instead of white, and his magic eye glows green instead of blue (though not in the soul color for kindness, which many get fooled by). He is also larger than sans from undertale by a good head or so, and can be prone to violence and a destructive attitude, unlike his undertale counterpart.
UnderRuin sans, as mentioned, looks very similar to his undertale counterpart. he is a big boned skeleton with the same clothing style and general shape as undertale sans. he is also slightly taller by a head or so, standing roughly 5 feet tall. both his eyes are defaulted to green, but his left eye blazes more intensely when using his magic while the other pupil disappears (like undertale sans). He has a crack across his right eye socket, which it's origin is unknown (though it theorized that he got it from using his signature weapon the Chaos Blaster).
He wears a thick, black winter jacket with a grey, fur trimmed hoodie (note the fur is more ruffled than classic sans), and neon green drawstrings. when wearing a shirt, it is usually either solid black or solid green, though he has been known to wear just the jacket over his ribs. his shorts have a bright green stripe running down the sides, instead of a white one, and he wears either light green slippers or dark black-with-green sneakers, usually untied.
UnderRuin sans is a more sinister and darker version of undertale sans, but still retains his love for puns and comedy.
He is known to be deathly serious and extremely powerful, though he usually bounces back with a grin and pun before people can understand what he said, similar his undertale counterpart.
Ruin sans still shares alot of his personality with his undertale counterpart, being a lover of comedy, extremely serious at times, being lazy and having a secret hatred for humans. though with him, it's probably not that much of a secret. His world doesn't have a human of it's own but he constantly hints to his despise in his 'jokes' or comments. his hatred comes from the fact that he blames humans, partially if not mostly, for the current state of ruin the underground is in. this could be because he believes Frisk left them after fighting flowey and never returned to save them ( see more about this under his story).
he is extremely withdrawn and highly mistrusting towards most characters, taking on a lazy, laid back personality and spending most of his time alone. he can also be very impulsive and aggressive when he feels his friends or himself is threatened.
Powers and Abilities
In UnderRuin, sans is far more powerful than his undertale counterpart. he shares the same powers as undertale sans, such as being able to telekinetically control a human and monster soul with ease and form sharp bones with his magic. He can manipulate Gaster Blasters, the number being quite massive (10 total), and has the power to teleport. however, he can summon all his magic together to form a massive Blaster he calls the 'Chaos Blaster'; a towering dragon like skull that is three times larger than the average blaster.
The Chaos Blaster:
the 'Chaos Blaster ' has two extra eye sockets above the original pair as well as an extra pair of nasal passages (nostrils), all of which glow a sinister green with a slit pupil. sans only uses this as a last resort when it is ABSOLUTELY NECESSARY because it takes up so much magic that it causes him to faint for a few minutes afterwords. it's so powerful that, similar to the hypergoner used by Asriel in Undertale, it drags in all magic around it, which coalesces into a bright ball of energy within it's jaws, and fires a beam of magic strong enough to lay waste to an entire kingdom (leaving it in ash and dust) and drag in every single timeline to charge it's power. it can also drag a soul into itself ( since it pinpoints all magic in the area to charge it's beam.)
The Start of UnderRuin Begins about one year after the events of the last Nuetral Run. In This Alternate Universe, Flowey is the ruler of the underground, and even more than that, he is finally GOD. After battling frisk, they were so weak from the constant loads that he eventually managed to absorb their soul, and with it Chara's being. Doing so made him far more powerful than he would have been otherwise with frisk alone. He went on to reset the timeline and,by having the power to load and save (which shouldn't be granted to him) planted a virus into the world's code, forming an entirely new AU in the process. The World of UnderRuin is dark, both literally and figuratively. all the monsters that Flowey brought back have no memory of their past life as Undertale characters and,worse yet, have lost all sense of emotion such as love, joy and friendship, including sans. it is just the kingdom for Flowey to rule, to have a people who are blind to truth and cannot feel much of anything but apathy. all monsters believe humans are the cause of the current state of Ruin in the underground and blame Frisk for the destruction of their lives, due to belief that frisk left them, but no one does more than sans.