Inversion

Inversion is the third and final victim of Photo-Negative Gaster as well as his puppet, also deemed by him to be 'TNEMIREPXE LUFSSECCUS TSOM YM.' While being the last of PNGaster's experiments, he is also the most powerful of the three victims, which will be explained later on in this article.

Backstory
Inversion's story begins in an AU by the name of "RevertSwap," during a True Pacifist timeline where the human child has already broken the barrier so that all the monsters may dwell peacefully on the Surface. Sans was busy selling some of his homemade burritos in a food truck that he had rented for the day. He had just served his last customer for the day, which was of course, the human child. "thank you for your business, frisk!" The skeleton would call out to the child before stepping out of the vehicle, he would then use his teleportation magic, or how he would call it, 'a shortcut,' to quickly travel back to his and his brother, Papyrus' home.

Once he conjured his teleportation magic, he would realize that he was very much not in his home at all, he was, in fact, in a desolate white room with a black floor. "hey, this isnt my home! oh well, must have taken a wrong shortcut, heh!" Sans would think to himself before he began to wonder what could have possibly gone wrong with his magic to have made him end up in such an empty place. Though, it wasn't as empty as he had initially thought, behind him was what appeared to be some kind of monster which looked to have had it's colors completely inverted, Photo-Negative Gaster...

"...EGDELWONK YM OT ELBUORT YNA TUOHTIW MOOR NOITATNEMIREPXE EHT NI PU DEDNE SAH TNEMIREPXE TXEN YM ,STLUSER GNISAELP GNIWOHS SI NOITALUPINAM CIGAM EHT TAHT SRAEPPA TI..." The figure would announce aloud as if it were recording something down for future use. "hey chum, do you know what this place is? i dont believe ive ever been here before." The skeleton would try to ask the strange figure, which would ignore him. "...no? ah, thats fine, i can just take a shortcut back." Sans would respond to the silence before attempting to teleport to his home again... which would end him up right back into the desolate room. "...WON EGASU CIGAM RIEHT REVO LORTNOC ETELPMOC EVAH I TAHT NOISULCNOC EHT OT EMOC TEY TON SAH NEMICEPS EHT TAHT SRAEPPA TI..." The figure would echo again before teleporting up front to the skeleton without any warning whatsoever. "hey pal, youre uh, being kinda creepy, to be completely honest. do you know how i can get out of here?" Sans would try to ask the figure again before a couple of gigantic floating black hands with white holes in them instantaneously materialized from thin air, gliding toward the confused skeleton. "woah- hey, i dont want any trouble!" Sans would shout out as he collapsed on the ground from the sight of such big hands, trying to shuffle away from them.

"...NIGEB DNA DNUORA GNILOOF POTS OT EMIT SI TI ,EROMREHTRUF ...ELITUF SI NOITATNEMIREPXE SIHT MORF EPACSE OT STPMETTA RIEHT TAHT DNEHERPMOC OT MEES TON SEOD OSLA NEMICEPS EHT..." The figure would say to itself before summoning a third, smaller hand behind the skeleton before it bashed him right over his head, creating a gaping crack at the top of his skull. Sans would, of course, be put in a state of unconsciousness after the blunt trauma to his skull, allowing the figure and it's hands to do whatever it pleased to him...

Once Sans began to wake up, he noticed that he couldn't see anything, he had literally gone blind! "wha..!? what happened to my eyes..!?" The skeleton began to enter a state of panic and confusion. "...NOISIV LATNEM FO TFIG EHT TI NEVIG EVAH OT SMEES DNUOW S'NEMICEPS EHT MORF GNIDURTORP HTWORG LARUTANNU EHT TAHT WOHS SEIDUTS YM ,NOISIV LAMRON FO ELBAPAC REGNOL ON SI TI HGUOHT ...STLUSER GNIYFSITAS EROM RAF DECUDORP SAH TI FO SSEL GNISU TAHT SMEES TI ,̷̢̢̧̢̰̝͇̣̠͙͚̭̭̣̝͚̘͕̼̯͎̓̓͑̂̇̊̈́̀̑̎͜͠|̸̢̛͕̰̣͕̳̞̝̹̭̜̯̞͚̣̔̈́́͂̈́͑͊́̑́̀̐̈͘͘̚͜͝͠|̸̢̲̯͚͉͚͖͔̥̀͑̾͋|̸̫̥͖̭̞̫̻̹̟̭͑͂̑̈́̏͐͆̀̚͜|̶̡̛͉̹̣̲̆͂̏̍̀͗̆̈́̿̓̿̀̈́̈̉̓̎̄͘͘|̵̡̻̯̻͚̲̈́̈́̐͌̉͐|̸̨̧̢̫͇̦̻̱͙̲͖̯̰̻̲̤̰̽͊̄͌̅͘͝|̷̨̢̺̼͎͇͖̰̥͎̩̗͚̳͋̈́̍̀̐̏̅̍̂͑͐͒|̶̢̢̗̲͓̯͓͈͖͉͉̠͖̹̼͉͍̪̖͉̳̼́̓̐͒̈́̈̌̉̑͊̽͋̌̆̈̈́̒̕̕͠͝|̵̢̢̭̞͉̠̯͖̰͍̪̙̱̰͈̹̪̖͖̰̹͒͛̒̊̆̅̏͊̀̀̈́̉̐̏̌̈̌̚̚̚͘͜͝| HCUM OOT DESU DAH I ,TNEMIREPXE TSAL YM OT GNIDROCCA ...3 REBMUN YRTNE..." Although he couldn't see it, the figure had already stripped Sans of any color that he once had and then inverted his now-desolate colors. His eyes had been sealed up with excess bone marrow, which explains the loss of vision, and there was this unnaturally shaped looking white object protruding from the crack of his skull. The skeleton would begin to slowly find out that all of his vision had been directed into his mind, though rather than the vision being seen through the eyes, it was now being seen through the beacon that had grown from his crack. "what did... what did you do to me..!?" Sans would cry out, the figure paying him absolutely no mind. Out of nowhere, the figure's left eye socket began to glow in a black light, causing some kind of interaction with Sans' skull wound growth, inverting the colors of every single thing within the room. Afterwards, the figure's right eye socket would begin to glow, reverting the colors of everything back to the way they were.

"...SEITILIBAPAC EURT S'EGADNEPPA EHT TSET YAM I TAHT OS ,MOOR NOITATNEMIREPXE EHT MORF NEMICEPS EHT TCEJE WON LLAHS I ...SSECCUS ETELPMOC A SI NOISREVNI :TCEJORP TAHT MEES WON DLUOW TI ...DEDNETNI EVAH I YAW EHT TSUJ GNINOITCNUF SI EGADNEPPA EHT..." The figure would speak to himself as he summoned one more giant floating hand to descend upon the modified skeleton, as he got put through the hole in the giant hand, he would find himself to be put out in the middle of a completely foreign Multiverse. The figure was able to carefully monitor Sans' every action through it's vivid mental pictures, making sure that the appendage continued to function properly. Now, Sans lives out the rest of his days 'inverting' vast Multiverses as the figure's emotionless puppet...

Inverted HP
Photo-Negative Gaster's victims usually tend to gain this ability once he's finished experimenting on them. The negative HP behaves as positive HP, meaning that normal attacks only make the owner of said ability stronger, while healing attacks are dangerous to them.

Teleportation/Multiversal Travel
This ability is mainly controlled by Photo-Negative Gaster, this allows Inversion to teleport all the way to entire Multiverses. Although on his own while not being puppeteered by PNGaster, he can only use this well enough to travel to one universe at a time.

ATK Scaling
Inversion is still very well capable of using Gaster Blasters and bone attacks, though they have been modified thanks to PNGaster's experimentation on him. The attacks mentioned can affect both non-inverted beings and inverted beings, this can be done through the attacks doing a STAT check on the target before actually damaging them. If the check finds the target to be non-inverted, it will do regular damage to it, however if the check finds the target to be inverted, the damage will be changed to healing, being able to ignore the Inverted HP effect.

The Appendage
This ability is entirely controlled by PNGaster, he can simply activate the appendage's capabilities with the glow of an eye. He can flash his eye once to invert the entire multiverse that Inversion is in and also completely drain any and all color within the universe that he's in. While the inversion effect isn't permanent, as PNGaster can simply flash his eye again to revert the Multiverse's colors back to normal, the color draining effect is. Once a universe has had it's colors drained by this, every living thing within it will completely lose any and all emotion, with the exception of the beings within it that were emotionless to begin with. The inversion effect on Multiverses can completely alter how things happen within it, such as how blue attacks will transform into orange attacks and how white attacks will transform into completely harmless black attacks.

Trivia

 * Much like every other victim of PNGaster, Inversion cannot consume any food of any kind without it hurting him.
 * Inversion is almost completely controlled by PNGaster, most likely due to the skull appendage.
 * PNGaster has not done any further experimentation ever since the creation of Inversion.