This undertale AU was custom made by Ethananous512, and although he does not have a tumblr account, he does have a youtube channel. Check it out! (Keep in mind this AU is still in development and might have changes to the name of the AU, the names of the characters and other things. I would also appreciate if someone drew descriptions of the characters to post on the wiki!)
This AU follows the same story line of undertale, except, a certain character roams around the AU, and all other AUs.
Wanders around the AU, and secretly helps Frisk in the pacifist run, while stopping them in the genocide run.
He is the final boss of the genocide run, and you encounter him after Sans. In battle, he will absorb the six human souls and fight you after Frisk kills Asgore and Flowey in the genocide run.
In the pacifist run, he helps you defeat Omega Flowey, and will rewind time to help you fight him.
In the Asriel Dreemurr fight, Neil is trapped within Asriel's soul, and needs to be saved like the rest of the lost souls.
He wears a red hoodie, goggles, a black wristband on his right arm, black sneakers, deep blue jeans. He has deep brown hair and eyes, and has a Micronesian skin color.
Papyrus has changed a bit, as well. He can now remember through true resets and normal resets, if Frisk killed him or not. He keeps count, and the more you spare him, the more he will like you. However, killing him results in him distrusting you for a few resets, but eventually warms up to you again.
Sans now uses more powerful attacks each time you kill his brother.
Although Ash goes by Ash Evil, his real name is Ash Granger. He is Neil's twin, and has a thirst for monster dust and human blood. He will kill anything that he deems worthy of dying, and is the main antagonist of the neutral run.
Ash will appear after you defeat omega Flowey with Neil. He will call you both idiots, and that Flowey was just a distraction for you two. While you, Neil and Flowey fought, he ripped a hole in the space time continuum, so that every character from every other AU would come to this AU. This causes a disastrous space time malfunction, and after the game crashes and the player reopens it, Ash will speak to them almost magically. He says that everyone is getting along with one another, and that he wasn't expecting the game to only crash. Ash starts to say something about a magical power only you posses, but then the game automatically resets.
He is pretty much the same as Neil in looks, except he has deep black hair, a deep black jacket, dark gray jeans and black sneakers, and has goggles and a wristband, except he also has a shocking bracelet around his leg, but it is disabled due to him hacking into it and shutting it down automatically.
Ash also has an ULTRA FORM, but he does not reveal it until the true pacifist ending, where to tries to stop Asriel from destroying the barrier. Fortunately, six souls and all the monster souls combined completely disintegrate Ash's body, leaving him as a pile of black dust.
Mettaton/Mettaton EX/Mettaton NEO
Mettaton and Mettaton EX has different dialogue if you name yourself Ethan for the game. He will call you "Homie" instead of human, and will give you a maximum bonus of 2000 ratings. The original mettaton will actually let you pass through the play scene if you're named Ethan. Mettaton NEO will ask why you've come to killing him when you are named Ethan, and ask you why you stopped being the "homie" he once saw you as. He is still killed in one hit. (These are easter eggs, hence the name "Ethan" Also being the creator "Ethananous512".)