Nightmare Sans: He has an okay relationship with nightmare it's not a hate relationship nor is it a like or love relationship. He still loves puns but he tries not to annoy anyone with them unless he's accompanied by another pun loving Sans. He used to be very laid back until he had to fight Error, and started to roam the AU's. Shadow is very kind, but after his world is destroyed he becomes slightly paranoid and a little more depressed than the usual Sans. He also has Gaster Blasters but they aren't that big. He has very weak KARMA, and can't really use it. Also has light green magic, again Shadowtale opposite of light blue magic. He also has green magic, in his universe it's his alternative to blue magic, to keep a soul still for a limited amount of time in or out of battle. Shadow teleportation majorly effects him when going long distances, and he uses them as 'shortcuts', just like any Sans, but he becomes very tired after teleportation. He has black bones that can form from the ground, from the shadows, sometimes appearing as light green. He can travel through universes by going somewhere with some sort of shadow and form from the light of an AU, this magic weakens him a little bit. He can travel through shadows like teleportation, and quickly travel across light but can't stay in the light unless he wants to get back into solid form, his soul isn't touchable or detectable while in the using this power, which is the reason why Error couldn't destroy him along with the fact that he knows to use the power draining powers when he really needs them. He has usual Sans power but a lot of them make him weak. Also he has a gold tooth that he got from Fell from their first meeting. Shadow blushes when Lust does anything flirty or caring because he's never really used too anyone but brother and Calina to care for or love him. Sometimes he ties his tie when he's around Lust Sans, and Lust usually ties it when it isn't tied, when Lust does it, he makes Shadow blush light green, just because Lust thinks Shadow looks cute when he blushes.
UNDERTALE AU INK SANS FIGHT CRACK
He has one crack under his right eye socket in a left to right curve motion, and a crack above and below his left eye socket in a left to right slash motion. His right eye constantly has a light green eyelight while his left one is always black even when he's angry. Shadow is a few inches taller than a normal Sans and wears a long sleeved white shirt halfway tucked into his pants, with a light green untied tie, black blazers/pants, a black belt with a dark green buckle slightly undone, black boots that have light green buckles, and a black cloak with light green stripes coming from the top middleish part of the hood and goes down. Nightmare visits Shadow in his dreams occasionaly turning them into nightmares if Shadow rejects his offers. Sometimes, on the rare occasion, he leaves Shadow alone. Shadow mainly visits UnderLust and UnderFell, but sometimes visits Ink Sans, and Dream. Flowey, Chara and Frisk stay in the Omega timeline while Gaster and Shadow explore the universes, Shadow occasionaly checking in on Frisk. His soul was corrupted by the death of his soulmate Carina. He received scars from both the Error fight, and the Monster Human War. Shadowtale Sans fought Error so that those who knew to escape, could escape, he tried getting his brother Papyrus to escape with Frisk, but Paps was determined to spare Error, which led to him dieing, and weakening Shadow's soul. Shadowtale Sans, or Shadow as he likes to be called, escaped the destruction of his universe, which was by Error, other escapes were his dad Gaster, Flowey, Chara, in spiritual form, and Frisk. Core Frisk knew Error was going to attack Shadowtale so they helped Shadowtale Frisk summon Chara, and collect Flowey then they escaped to the Omega timeline, as well as told Sans, Gaster escaped Shadowtale void to a different void before the attack and sometimes watches his son when he can.