Eyrick was sitting around casually in his apartment one day, living a normal, boring human life.  The usual stuff; go to class, eat ramen, stay up late playing Splatoon or whatever.  He ate breakfast in the morning, lunch around noon and dinner closer to 8 than to 6.  He folded his underwear, rolled his shirts and kept everything relatively tidy (except when his parents called him unexpectedly, saying they'd be over in 15).  He lived a relatively uneventful college life; keeping to himself for the most part.  He did have one caveat, though - the human had recently stumbled onto a resource on 4chan's /poss/ board.  /poss/ standing for possession, that is.  People were recalling their experiences with shadowy figures, attempting to channel the spirits of the underworld, and a whole host of other things that typically were discounted as fake and gay.  One such "expert" on the website, however; had seemingly developed a method of creating your own creatures purely off meditation and one's own chi - aka, 'body energy'.

The article Eyrick kept reading had a number of videos of the guy creating small, glowing energy orbs that quickly took anthropomorphic forms of various creatures to help around the house; doing chores and other mundane tasks.  It seemed like a legit-enough strategy, since there was tangible evidence that it worked!  Eyrick had talked to the guy back and forth for a while now, and he was confident he could gather up enough energy to get the same effect.

Eyrick sat down in the middle of his apartment living room; having turned off all his electronics and whatnot.  The sun was kind today; it beamed brightly through his 13th-story window onto his face.  He crossed his legs and unfolded his arms, bringing middle to thumb in a typical meditation stance.  In his head, he thought of exactly the same things that the guy on 4chan had told him to do - nothing at all.  Deep breaths ensued as the quiet of the room quickly began to take hold.  Eyrick could feel something welling up within his body, but he wasn't exactly sure what just yet.  Suddenly, the human found his trance broken by a fart MUCH longer than he'd ever done before; fifteen seconds of carpet-rustling gas that blasted him into the air and straight onto his face!  He even levitated just for a second or two before the ass-gas ended and he was left reeling from the comedic impact.  

"Jeez... this stuff really works, huh...?  I've never had such bad gas before!"

Eyrick shook off the impact and went back to sit on the floor again, pooting once more before his rump calmed down.  The human realigned himself with the room and took to silence again.  In his head, he had a vision of a familiar game - Minecraft.  Something was hitting him from behind, however.  He spun around in his head to find a terrible stomach-shaped beast trying to devour him!  His blocky, subconscious self ran away and hid in a hole in the side of a mountain - a loud *PAF* came out from the opposite side while the quadropedal mouth-beast spoke deeply and malevolently:

"Just eat something."

Eyrick immediately jolted from his trance again, coughing and sputtering just a bit from the vivid, yet intense daydream.  He was a bit shaken by it all, and suddenly he found himself rather hungry!  He got up, swearing off the whole thing while he took to cooking some ramen in his kitchen around the corner.  The 'whole thing' wasn't swearing off from him, however.  That cloudy, wispy fart from earlier suddenly took on a more congealed, translucent brown human form itself!  It walked around the corner, peering at Eyrick's ass while he bent it over top of the kitchen counter and flashed a dirty, mind-numbing grin at the unsuspecting human.  A strange crease had started to form underneath Eyrick's shirt as well... and an ominous gurgling told him to 'hurry up and eat something' - literally.

Eyrick's tummy gurgled as he pondered over all the food he had at his disposal in his kitchen - pasta, ramen noodles, and some veggies scattered through the cupboards.  Laziness just defaulted to ramen for him, usually, so he decided to go for that.  He grabbed a pot, filled it with water, and set it on the electric stove to get it boiling in a hurry.  Eyrick kept hearing his stomach gurgle every few seconds now as he chucked the package of noodles into the pot and let it boil up.  His tummy rumbling got worse and worse in the middle of cooking, however; so he decided to add another package along with more water to make more broth for it to sit in.  Once the noodles were done, he got out a serving tray so he could watch TV while he ate his food.  He let a rather foul-winded fart out in the process; chuckling to himself after he caught wind of it.  Fortunately, living alone meant that only he'd have to deal with it; his apartment was already fairly musky as it was, and opening the window usually fixed that issue with time.  He grabbed his bowl of noodles after pouring them out of the pot and sat on his futon-couch in the living room space of his apartment and started to spin them around his fork.  Eyrick lifted the food up to his mouth, and no sooner did it touch his lips did an almost demonic voice bellow out from his gut:

"Wrong hole, moron!"

Eyrick suddenly felt a surging pain rip through his arm that caused him to drop his fork back into the bowl.  In a panic, he suddenly lifted his shirt... and the crease underneath had grown into a gigantic mouth!  Eyrick hadn't even felt the thing start to form, let alone notice the wet spot under his shirt; laden with drool!  The mouth on his stomach opened up wide; showing guts and other internals that he really typically shouldn't!  That cavernous belly of his extruded from within a large, pink and very wet-looking tongue!  It dipped into Eyrick's food, lapping gently at the broth and dragging a few noodles in past the toothy grin it showed afterward.  While all this was going on, the gassy creature peering out of Eyrick's bedroom sauntered his wide, bulbous hips around the two corners and laid his arms on the back of Eyrick's couch.  The human was only aware of the one creature inhabiting him at that point; aside from the smell of his own gas still being fresh in his nose.  He watched as the belly monster opened up wide, and felt the urge to feed it growing stronger and stronger.  Eyrick gave into the urge and poured the entire bowl of noodles directly into his newfound gaping maw; tasting it on his own tongue as the mouth-beast gobbled it up!  The flatus-creature giggled slightly to himself as he watched the other two have at it.  Eyrick stood back up again as all this gluttony had gotten his dick a little stiff, but he wasn't done just yet!

"MORE FOOD.  WE WANT MORE!"

Eyrick nodded a little nod as he went back into the kitchen; his eyes dilated a little bit in a mind-numbed trance.  The gassy monster followed close behind, rubbing Eyrick's hips and keeping his nose fart-scented for now.  His eyes glowed with a fiery, wisp-like cyan texture as did his teeth, and being a gas, he could slip a hand down the back of Eyrick's jeans without the human noticing!  He started to fondle between Eyrick's buttcheeks with his right hand down his pants and his left hand on Eyrick's left shoulder.  The human grunted numbly as the gassy creature got extremely close to his ear, making silly fart noises into it.  At the same time, the creature had gotten a finger or two inside of Eyrick's ass, filling it with nasty-smelling turd gas!  Eyrick went along with it while he took to the fridge - lots of leftover pizza was there to munch on!  He began to remove a box, but the mouth beast wasn't having any of that; it chewed up the box; pizza and all!  Eyrick bleghed as he didn't particularly like the taste of cardboard and ink, but the pizza more than made up for it!  He rubbed his tummy and suddenly caught a boner when the mouth beast decided to chew and gobble on his hand, too!  The gassy human was in such a state of flux that he had to give his ding-dong a tug or two.

"Naughty boy.  Shouldn't you be eating, still?"

The shapely fart beast behind Eyrick made him nod as he took his wet hand free from his belly; all that pizza and noodles having already found themselves as big clods of junk food in his bowels by now.  This seemed like a great time for a grocery store trip in his head!  (Or at least to Golden Corral or something.)  The nasty-smelling creature at his backside followed him back into his room as Eyrick got dressed, but he'd be taking on a less-visible viewpoint from there.  It wouldn't do for your best friend to get thrown out because he smells like ass, would it?  Eyrick tensed up as he felt the fart monster invade him through his asshole; the actual fart portion making his bunghole gape a little bit as there was a lot of gas to shove up in there!  The mouth-shaped monster bleghed a little bit as it retracted its tongue into Eyrick's abdomen; somehow able to taste the gas in its mouth as well.  And poor Eyrick bleghed as he suddenly belched from his own face; sending a gush of stinky gas the wrong way!  He huffed and hurried up getting dressed and took off for the nearest grocery store a few blocks from where he lived.

It was fairly packed for a Monday afternoon at the store; there were about twenty or thirty other people shopping that day.  Eyrick grabbed a cart, but he wouldn't need it with that ravenous mouth beast wanting to eat out the entire store - produce, perishables and people alike!  Eyrick walked like a zombie as he filled his bowels directly from the store shelves, ripping open boxes of Cheerios and (somehow) finding the strength to pop open cans of cabbage and greens with that mouth port of his down below.  He had taken a bit of an evil grin himself as he went along chewing up the store's not-so-hard-earned pineapples, but one of the store clerks caught him doing as such.  The man walked over to Eyrick as he shoved a watermelon directly under his shirt!

"Hey; where do you think you're going with that?"

Eyrick spun around with cyan-glowing eyes; a zealously fueled fire rippling off his eyelashes.  The man immediately took a step back, but it was far too late for that.  Both monsters spoke while the gassy one kept gushing into the air; foul and funky!

"Where do you think YOU'RE going with YOU?!"

Eyrick perked his tush directly outward and farted.  Sharted, even!  The human created a gas cloud that warded the curious from inside and knocked the man out cold.  Eyrick drooled from both mouth ports as his boner rose upward; losing a spot of control down there as prespunk started to ooze from the tip of his dick.  He was gonna enjoy filling his gut with the unwary human!  The mouth beast opened wide; and Eyrick shoved the man inside without a care in the world.  He curled him up as best he could, but chomp chomp *BELCH* still happened.  The cloud began to dissipate, and for a few seconds Eyrick could feel his skin stretching to fit the human inside him.  Thick, goopy brown drool came from his own natural mouth as the beast digested and excreted the human in a huge pile that made the fart-monster below inside Eyrick's anus moan lustily.  Inside, he also had a tongue; albeit a less corporeal one; letting it drag over the human's beefy, brown turd.  Eyrick crapped his pants and hunched over, pissing in them as well for good measure.  (Pineapple juice is good for virility!)  The human watched the produce aisle clear out as more humans caught wind of what he'd done, but he wanted MORE MEAT.  Eyrick suddenly dropped to all fours and dug his nails into the ground like a feral beast in heat and bounded from the floor to the ceiling, bouncing off it and immediately pinning another human in the meat aisle!  A few screams and a fart cloud later, and Eyrick had another hundred-pound load to get rid of.  The mouth beast made him lean into the raw beef, sausage, pork; everything!  All it did was drop its jaw while Eyrick ran along the inside of the freezer; knocking metal shelves down and making a general biohazard of the place.  

The HVAC had started to pick up Eyrick's gas as well; recirculating it through the building as the fartbeast made more and more of a mess inside Eyrick's tattered jeans.  His butthole had grown rather puffy from the shitfest that was following each human going down through his bowels in a matter of seconds; turning everything into brown, mushy shit!  The worst part of it was that the people in the store couldn't resist fainting due to the power of the stench in Eyrick's butt now, so given a few more minutes the store would look like someone hit it with a biological weapon of some sort!  Eyrick gobbled human after box of cereal after woman after child after store manager to the nasty, off-brand Pop-Tarts that no one will ever eat.  Yet his figure stayed the same; albeit more mind-controlled than ever!  Eyrick snorted as he grabbed the last human in the back office of the brown-clouded store, stuffing him into his tummy.  The human groaned a little grunt as one more disgusting blast sent an equally disgusting coil of shit spiraling through ironically the cleanest aisle in the store - the mouth monster didn't really have a taste for household cleaners, apparently.  Eyrick himself actually wanted to keep going with this vorish crusade, but being so satiated, both monsters inside him needed a break.  Human libido can be difficult to keep up with!  The gassy one was the first to exit, however; as Eyrick lay on his side; tongue flopping against a pile of his own turd.  The mouth monster did the same, and Eyrick rolled onto his back while the salacious fart beast extruded itself out of his butt with the next pile that the human spewed out.  

"Ugh... what a nasty guy you are."
"It's -- your fault -- !"
The mouth creature gurgled and suddenly spit out a femur or two against a couple mops, sending them crashing to the floor.
"I can't keep up..."
"That's -- your fault!  Jeez..."
"Heh... if it weren't for me farting all day there'd be police swarming this place by now; I'm sure of it."

Eyrick leaned up and thought about it for a second while both creatures' sway over him started to wane a little bit.  He'd just committed vorish genocide and suffered little consequence; if for having put on a couple pounds around that tush of his was one such thing.  The human gurgle-burped once more as his stiffy continued to stay as such with the mouth monster continually licking at it!

"Hrf... so I know what YOU look like... what's mouth-butt down here look like?"
"It's probably better *shlurp* if you didn't know.~  I'm gonna go to sleep."

The mouth beast belched loudly and sunk its teeth back into Eyrick's gut, along with its tongue as well.  It closed its lips, forming the crease from earlier and rounded Eyrick's belly back to normal again; belly button and all.  The human sat; somewhat confused, but he was still a touch too horny to care.  That; and the fart monster was still there as well.  His cyan eyes glowed and a long, demonic tongue darted across his lips while he looked at Eyrick's dick.

Eyrick groaned in the moments afterward as the gassy creature became just corporeal enough to lift his legs off the warm, poo-stained grocery store tile floor.  His dick was much like Eyrick's in length, but girthwise he had at least double what Eyrick was packing.  He intended to fully use it as he shoved into Eyrick's ass, causing the human to yelp and groan softly to himself!  An easy rhythm built up as his already gross and gaseous dick plunged out the rest of Eyrick's shitter; making him poop with every thrust that pulled his swollen bunghole back out again.  Eyrick felt his already-teased dong throb and leak with precum and a little piss from earlier (the milk was finally getting to it); he wasn't going to last very long with such treatment!  The fart monster quickened the pace; making tinier, squeakier farts erupt from his dickhead.  Eyrick's butthole looked like it'd seen ten years of 'usage' by now, and was getting worse and worse as the beast filled him with more gas, just like before; only sexier and smellier!  He couldn't take it anymore; surging a cumshot that could be seen two aisles over!  Eyrick gushed for thirty seconds straight as the pressure eventually died down.  The beast finished up in his ass, but held onto the 'jizz' he had so he could spray what felt like liquid fart onto Eyrick's face.  He only took a few seconds to do that before he sat on Eyrick's face; the human instinctively licking at the foul, corporeal air in his mouth.

"Give us a call if you ever wanna do this again, hon.  You've got such a wonderful brain; I'd hate to see it -- go to waste!"

The bad pun signaled the end of the flatus beast's existence in the world - with a grin and a chuckle, he pooted once more in Eyrick's mouth before disappearing into a cloud of gas!  The room's tinge started normalizing as he dematerialized, and the cyan flames that engulfed his mouth and eyes dissipated as well.  Eyrick leaned up as two marbles and around twenty or so glass teeth clattered on his ribcage.  They fell to the floor as he got himself back up again, opting to exit through the back door this time to avoid any unwanted attention.  Eyrick walked home briskly and quietly - he REALLY needed a bath!