Drawing to go with a story by nothere though slightly not in the order it happens into the story because I'm apparently slightly illiterate.
Reginald Gigacksian, esq., had made it his life's most personal mission to describe every living thing in a grand book. He called it the Abominable Bestiary, and it was called this for two reasons. First, Reginald hoped to get the hardest parts of the book out of the way first, so he began with the most bizarre and difficult-to-find creatures in the multiverse, combing the ends of the earth and many of the diverse alternate planes of existence. Second, the name "popped" and promised to sell well.
The book was arranged either in order of rarity or order of weirdness, since the two were often one and the same, and Reginald was in his study in The Berwickshire, snappily dressed in shirtsleeves and working on an entry for a Malicious Dink (pg. 447) from the Ethastral Plane (or possibly the Elemental Plane of Boogers, more research was needed). One was splayed out on a rig for dissection, which was exceedingly difficult as Malicious Dinks were totally insubstantial and could only be held in place by nonexistent pins and cut with knives that never were--both of which were harder to acquire than Equatoguinean Peryton eggs.
A soft rapping came on the door, startling Reginald in mid-fountain stroke. "What is it?" he cried, reaching for the blotter. "Does 'do not disturb' mean something rather different where you come from?"
"Sir, a package for you has just arrived." It was the help, Reginald's faithful manservant whose name he had never bothered to learn.
"Very well, bring it in."
The package--which the help left on the desk before scurrying away after placing a bowl with snacks nearby--was covered with postmarks from stem to stern, but Reginald recognized the name. It was from his colleague Oliver Whitford in Egypt, the same one who had sent over amazing preserved anolamocarid (pg. 38) tissues some time ago, despite the fact that the latter creature had been extinct since the Permian. This package, though, had a telegram attached:
"KNOW YOU HAVE BEEN SEARCHING FOR HOLLYPHANT FROM ELEMENTAL PLANE OF SUNSHINE STOP BELIEVE HAVE PRISTINE SAMPLE THEREOF ENCLOSED STOP TREAT WITH EXTREME CAUTION AND IN UNDER NO CIRCUMSTANCES ALLOW TO BREAK STOP"
Reginald's eyes widened and he let out a gleeful yelp. He'd been searching for a hollyphant, or even any trace of one, for ages. Supposedly residents of the Elemental Plane of Sunshine, they were hairy elephant-like creatures with pixie wings that supposedly stood for all that was good and kind and sunshiney in the world. Needless to say, Reginald couldn't wait to vivisect one. Opening the package, he excitedly tore through many layers of wrapping only to find…
…that its contents had broken in shipping. What looked like a crystal sphere lay within the box, broken into several large and jagged pieces. Ignoring the telegram, Reginald immediately thrust his hands in to see if he could find the hollyphant bits that had been--that must have been--sealed in the sphere. Instead, his hands came out dripping with a strange liquid; annoyed, Reginald went to clean them off but as he reached for a towel he saw that his skin had somehow absorbed every drop of it in milliseconds.
Disappointed but not surprised at the clumsiness of the Royal Mail, Reginald prepared to turn back to his writing when when a sharp pain suddenly and intensely pain tore at his his chest as if digging from the inside out. He stood up and violently backed away from his desk.
"Urk!" Reginald gave out a strangled cry, and clutched at his chest, but the sensation only intensified. Instinctively, his jaw locked while his pupils shrank to pinpricks in eyes quickly widening in an expression of shock. "Was that…was that poison? Did I just stop my own heart?" He'd stopped his heart three times before over the course of his studies: one from a sting of a Sumatran Corpse Flower (pg. 22), once when bitten by a Greater Shade from the Negative Material Plane (pg. 183), and once deliberately in an experiment that would have absolutely worked if his assistant hadn't stopped him. But, painful as the blinding jabs were, now accompanied by queasy throbbing throughout every fiber of his being and some fibers he didn't even know he had, they felt different than his previous heart stoppages; something was clearly different this time.
"URK!" As things got more and more sore, it became clear with a fresh wave of pain and throbbing (with nausea to taste) that the something different was…Reginald. He could feel his ears twitching, but not just that; each twitch left them considerably enlarged, weighing down both sides of Reginald's head and growing more so by the moment ago, and visibly growing. But it wasn't just growth…something else was hidden in that deeply wrong feeling that wasn't quite a heart stoppage and yet not quite a possession from the Ethastral Plane (which had also happened to Reginald three times, but oddly all from the same malevolent spirit being). He could feel it creeping in around the edges of his ears, his extremities…it looked like some horrible kind of spreading contagion, like the Purple Death spread by screamer sporelings (pg. 111), at first. For a moment, everything became clear: it was hair, and the essence of the hollyphant was reshaping Reginald into something that resembled it. But that certainty was dashed mere moments later, when Reginald saw what was actually happening: his skin was extruding a thick teal slime from every pore and follicle even as, underneath, it was taking on a new shape.
Reginald had, in fact, uncovered the essence not of a hollyphant from the Elemental Plane of Sunshine but its opposite, the yin to its yang: a muckophant from the Elemental Plane of Tentacles. It would make a thrilling entry in his Abomimable Bestiary…assuming he still has thumbs when the essence was through overrunning his material form.
He clutched tighter at his chest, at his rapidly gooifying heart, as further sensations, each more slimy and unsettling than the last. A slime bridge ran between the last two fingers of Reginald's outstretched hands, sticking them together first with a web of ichor and then pulling and fusing into a single thick and mucky digit; as they became fully fused and fully coated with fresh-exuded slime, each of the four surviving digits swelled to match, sweating out great gobs of slime for the same slick teal patina that was beginning to appear in patches all over Reginald's arms, and his ears, and his back, and his…everywhere. His arms started to bulging, too, thickening and gelling near his rapidly changing hands, near his shoulders where his shirtsleeves were already beginning to stain and strain under gooey assault from beneath, and all points inbetween.
Beginning to press outward from the beneath his outfit, Reginald's stomach was wracked with fresh pangs--almost like intense hunger, complete with agonizing, empty grumbling. He was swelling outward everywhere, with teal goo seeping through buttonholes and widening tears in his clothing and increasingly gelatinous flesh not far behind. He was in the midst of gaining a muckophant's worth of mass, straining every inch of fabric on Reginald's body like a failing dam with goo and gut threatening to overflow it and burst forth. Reginald's patent leather shoes squished as he rocked back on them; each burst from the pressure, revealing that the toes on each foot had not only fused much as his fingers had, but were going much, much further and becoming cylindrical slime bastions to support Reginald's new and greater girth (and a few residual pieces of muck-soaked socks and forlornly empty garters).His legs, too, were adding layer upon layer of slime and slimy flesh, swelling until the threadwork holding everything together began splitting. Legs thickening and oozing freshly extruded goo, splits tore open all along the length of his slacks while sudden addition of a gelatinous tail burst though the seat, tearing it completely away. His swinging cod, exposed, was already dripping cerulean slime from its tip; with each drop the shaft grew both longer and thicker, and the trail of slime it left on the floor was more than enough to track Reginald without the use of hounds.
Reginald could feel the normal mucus membranes of his nasal cavity straining to meet the newfound demand for slime, and it tickled him from the inside something fierce, enough to distract from the pain of muckomorphasis. "Hurk…grah…grrrahh…GRAH…GRRRAHH…CHOO!"
With that mighty sneeze Reginald's chiseled nose gyrated, flexed, flopped, and blew into a snotty proboscis, only about a foot long at first, which quickly acquired the same teal coloration as the other slime rapidly submerging what was left of its owner's skin. A second sneeze followed, and a third, and with each the new muckophant's trunk grew in width, in girth, and in the sheer volume of the trumpeting it produced.
Reginald's hands and legs kept swelling in girth, and his body was busy providing them with still more girth to support. Deepening and growing at an alarming rate, his chest scattered his buttons all over the room in a shotgun blast of horn discs, leaving only scattered rags clinging to his now completely teal and gooey skin by sheer force of adhesion. Reginald's ears had grown so rapidly that they were already almost as big as his head, so rapidly that they could no longer support their own weight. Atop his head, his once lengthy hair was down to just a few patches before it vanished, every last strand forced from Reginald's pores as they were commandeered for the production of yet more goo. As for the slimy cock the destruction of his pants had freed, it had taken on a mind of its own; even as it swelled still longer and widened about the base and shaft, it began to move. Instinctively, it jutted first straight out and then to either side, feeling the bits of torn cloth and small items cast from Reginald's pockets all about the room.
With a cacophony of cracks, and seemingly almost as an afterthought, a pair of limbs burbled up through the slimy muckophant flesh about Reginald's shoulders. They were like human hands at first, then like skeletal bat appendages; it wasn't until the weight of the slime forced a membrane across the grasping and growing strands like a snot bubble that Reginald recognized them for what they were: wings. Where the hollyphant had feathery birdlike wings, the muckophant that Reginald had now become boasted gooey flappers straight off the rare snotdragon (pg. 221).
His metamorphosis seemingly complete, Reginald tottered for a moment as the pain subsided but the squishiness did not. He was seized with a sudden hunger; in point of fact, he was suddenly hungrier than the Insatiable Gulper (pg. 77). Casting his eyes on a bowl of roasted chestnuts set out by the help, Reginald reached out at them, either knowing nor caring if he still had teeth solid enough to crack them. Instead, goo surged from his sides, lashing out as temporary pseudopods to seize the foodstuffs and spirit it back to their master. The tentacles retreated back inside him with a wet splortch; moment later, he tasted nuts. A belch followed; Reginald wasn't quite sure where it had come out, but he heard the inedible shells falling to the ground coated in protective cerulean slime a moment later.
Slurping over to the desk, Reginald took up his fountain pen and began to write a fresh entry on a slime-stained page, ignoring the hunger pangs. Not long into the entry, a tentative knock came at the door.
"Sir? Are you all right? I heard noises, and something's dripping from the ceiling downstairs!" It was the help.
Reginald thought about shooing him away out of concern for how he'd react to the sight of a muckophant in the house, but then a fresh wave of hunger made itself known, and Reginald smiled beneath his new trunk. "It's open," he said. "Come on in."