sAnITy is a descendant of Zalgo whose debut and only canonical appearance so far is in Nightmare Shorts: Recall. He only exists in the "X-Dimension".
Nothing is known about sAnITy's past other than that the X-Dimension that he lives in is corrupted by a Zalgo virus.
A long time ago, the dying Zalgo released its virus. This virus was made up of corrosive, negative Chaos energy. Zalgo was filled with hatred for everyone, and this hatred mixed with the Chaos energy within him. When the energy escaped, it turned into a virus, infecting many worlds. All living things mutated into terrible monsters.
The Highests and Demons were able to stop the virus from spreading. But already infected areas could not be destroyed. Therefore, they were moved to a special "X-Dimension" that is separated from all dimensions and where all infected live ones are located. Although after infection, they are difficult to call alive or dead.
He first appears in the form of Sonic when Tails is walking alone after Knuckles gets teleported by sAnITy's Tails form, in which he proceeds to approach Tails and teleport him to a world reminiscent of the "Sonic 2.exe" trilogy games. When Knuckles goes to search for Tails, sAnITy's Tails form appears and teleports him to a world where physics are broken and he can only talk in Windows pop-ups.
When Tails stops running and looks at the night sky, it shows a constellation of sAnITy's Sonic form. Then later, when Tails loses sight of Inner Tails and is about to enter a giant ring, sAnITy's Sonic form appears behind him, but then he gets killed by Inner Tails' plane. After Tails enters the giant ring, sAnITy's Sonic form is there and starts to approach Tails again, but he gets pushed away by another copy of sAnITy in the form of Tails before he can do something.
When Tails is chasing Tails Doll to get the Time Stone, sAnITy's Sonic form flies towards Tails before teleporting him into various worlds. Later, when Tails and Knuckles are being teleported into various other worlds when trying to catch Tails Doll, sAnITy's Tails form is seen in the world where Knuckles has a white outline around him. After they are brought back from these worlds, sAnITy's Tails form runs into Knuckles and pushes him away. Once Tails finally escapes, several copies of sAnITy fly towards him, but they all get knocked away by Knuckles.
sAnITy's final appearance in the episode has four copies, two of his Sonic form and two of his Tails form, before soon getting knocked away by Knuckles.
During the battle with Tails Doll, he creates several copies of sAnITy in the form of Sonic to make it harder to beat him. If a playable character interacts with one of such copies while having no rings, it will kill the character and jumpscare the player.
sAnITy has no sense of self-preservation, and will attack anyone he feels like, even if it guarantees his destruction.
sAnITy has no physical form, but he has two forms, taken through Tails' memories.
The first takes the appearance of Sonic, but with duller and darker fur, as well as black sclerae and three red pupils in each eye. He is constantly hunched over and smiling.
The second takes the appearance of Tails, but with yellower fur, completely black eyes, and a fresh X-shaped scar on his stomach. He additionally has blood coming out of his eyes and on his gloves. He runs on all fours in this form because it's faster.
sAnITy has the ability to teleport himself and others to his glitchy pocket dimensions, fly, and make copies of himself.
He can also corrupt mortals, demonized mortals, and weaker demons, as shown in the playable version of Nightmare Shorts: Recall. There, if Tails/Knuckles die either by the hands of sAnITy or get killed in his pocket dimensions, they become corrupted and inherit traits of their killer, like moving on all fours and an X-shaped scar on abdomen as for Tails, and lack of pupils in the eyes as for both Tails and Knuckles. Both of them also can't talk, just as their killer, and, just like him, cannot leave the X-Dimension.
- Sometimes his Sonic form is known as "Exodus", but Jaiz Koys has confirmed that his name is Sanity. The origin of the name "Exodus" is unknown, but it may be a scrapped name.
- Most likely, the appearance of his Tails form is modelled after the Zalgo-possessed Tails Doll from the "Sonic2.exe" trilogy. The only distinct feature of it is the X-shaped scar.