Toothless the Night Fury gets a day off to himself, but without Hiccup around, might get himself into an unexpected situation!

Request from  kirito467
I know I started it over a month ago, but it's my first time writing a slime story! Hope you enjoy :)

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Hiccup affectionately rubbed the Night Fury’s scaly head. “Alright, Toothless. Don’t go too far!”

The large, scaly black dragon purred and flared his wings for a second before taking a dive off the cliff. The wind coursed over his body as he angled himself back upwards and soared for the skies. He loved flying along the shoreline between the withering stone formations that rose from the sea, occasionally plummeting back down to drag his paws through the foamy surf. Since Hiccup had let him go flying alone, he could do it all day if he wanted.

As he passed by a tight curve along the cliffs that gave way to the sea, he spotted a dark area of rock. Coming nearer out of curiosity, it was quickly apparent that it was actually a cave, shielded from the sun, and he couldn’t resist landing on the edge and peeking inside. It was the perfect size and shape for a Night Fury to explore.

Toothless lowered his head and crept along the floor as he entered, listening for sound, but only the dripping of some condensation from the damp, stony ceiling could be heard and the changing pressure of the wind shifting over the entrance behind him. His body blocked out the sunlight briefly, but when he moved aside it shone brightly again to light up what turned out to be a rather cavernous space, with several smaller tunnels in the walls around him. He supposed the wind and sea probably carved them there, but didn’t think much else about it. He was just excited to look around.

There was some water pooled on the floor, which he splashed around in, his tongue lolling out of his mouth. He was having fun. He went sniffing at one of the smaller tunnels, watching a shallow trickle of water drain down it, but when he lapped it with his tongue it tasted of salt. He snorted and shook his head, his pupils widening as he looked elsewhere in the cave. There was a larger tunnel next to the one he’d just been playing with, and he saw that if he flattened himself to the cave floor, he could easily slip inside.

It was narrow, but widened into another cave, slightly smaller than the cavern he’d started out in. As his green eyes adjusted to the darkness, he noticed that there was more trickling water along the floor. He didn’t learn his lesson from last time. It tasted like salt.

His head bolted up at a strange, less familiar sound. It still sounded sort of wet, and he was sure it was just the dripping water making an echoing noise the further it trickled into the crevices of the tunnel. Still, some of noise seemed to be far closer, and he leaned forward to peer more closely around at the cave walls. He saw they were also covered in a more slippery wet substance in addition to the damp condensation. He hadn’t noticed before in the dark, but now he put out his tongue and took a big lick.

It tasted good.

A bit more excited than he had been at dipping his tongue into the salty water earlier, he took another lick. And then another. Soon, he was lapping up what he could find along the cave walls, his nose seeking out more when the thin coating seemed to run out. He snorted and shook himself when it was gone. There were cracks in the walls that he was sure held more, but he’d already poked his tongue into every place he could reach.

As he turned to go, however, he suddenly realized that there was more under his feet. He tilted his head. When had that gotten there?
He didn’t bother thinking too much about it as he leaned over to lap at the spot on the floor, feeling only grateful for his luck. It was so good, it was as if the slimy substance was practically leaping into his mouth.

Wait…

Was it actually leaping into his mouth?

He pulled his head back, realizing that it was pouring into his mouth more quickly than was natural, and strands of slime continued to hang from his jaw even as he stood up straight. It tasted really good, but he was alarmed by trailing slime continuing to pour into his mouth even after he’d reared back his head. How was this happening? He padded around the room, frantically licking his lips to get rid of the trailing slime, but it just kept coming. It also began to coat every surface of the cave more thickly, and he found more on his feet as he paced. It tasted amazing, but he found it strange and decided it was probably time to go.

He shook his head again to get rid of any lingering slime as he turned back towards the narrow exit to the larger cavern, even though he wasn’t quite successful. He crouched down before the tunnel. He’d have to crawl along the floor again to wiggle back out. He knew he’d be covered in the slime, but at least outside, he could plunge himself directly into the ocean and let it wash away. Maybe he could snap up some fish while he was at it—not that he’d be hungry!

When he put his head low to the ground so that he could begin to scurry back through, more of the slime was able to immediately pour into his mouth, making him growl slightly in surprise. He wasn’t able to pull his head back fast enough to stop it, and realized there was far too much to shake off anyway. Wherever it was coming from, there seemed to be an ample supply.

He decided that the next best thing was to just push forward and get out of here. His belly was starting to strain as it filled with slime. No matter how delicious it was, he could still only eat so much before he felt full, and he was quickly approaching that point now that the slime was flowing faster. He flattened himself to the ground again and shimmied forward in the cramped space.

Even as he moved forwards, trying to keep his mouth shut, it dribbled through his jaws and he felt his stomach swelling. The gap that he’d fit through easily before felt tight as he crouched low and pushed himself forward, until his back bumped the top of the gap and he was having trouble moving any farther. He realized that his belly had become so bloated that it was pushing firmly against the floor, and now the gap was quickly becoming too small. He wriggled a bit, his finned tail lashing as he edged forward.

The one good thing about the slime was that it was slippery enough to aid him. His belly was straining uncomfortably by now, but he was determined to get out. He practically had to at this point, or the mysterious goo would endlessly fill him. He kicked and scrabbled with his hind legs a bit to push himself forward again, feeling his rapidly filling midsection continue to swell, and edged closer and closer to the area where the cave widened back into the main cavern, where he could finally make his escape.

For a moment, as his belly tightened, he felt the stony surfaces scraping along his body almost draw him to a stop. The soft, squishy slime in his belly jiggled as he wriggled one last time and was able to force himself free.

Now that he was in the main cavern, he could stand up, ready to charge for the exit and make his escape. He realized how heavily his belly was hanging by now, and how flabby he was beginning to get as his body began to digest it. When he shook himself off, everything on his frame bounced with the motion. He took a few steps forward when he thankfully felt the slime begin to retreat from the floor. Finally!

A moment later, he realized perhaps he’d been relieved too soon as a collection of it began to deliberately pool on the floor in front of him. The sheer amount of it eventually piled up, growing taller and wider; Toothless stood and watched in fascination as it eventually took on a more deliberate shape. The wobbling lump of jelly rose up—and then shot towards him.

He opened his mouth in surprise, and that was where the goo immediately forced itself. He tried to back away, but it just kept coming, slithering down his throat as he was repeatedly forced to swallow. It still tasted as good as ever, but his belly was stretched painfully taut, and his body wasn’t digesting it quickly enough to help. His stomach had quickly become a rounded, quivering globe that he began rubbing at with his forepaws to relieve some of the pressure.

He couldn’t stop the slime from slipping inside his mouth, but he started forward again, knowing that the only way to escape the sentient creature was to leave, even as it continued to pour itself into him. However, the heavier he became, the harder it was to step forward, especially when his distended tum began to brush against the ground and the front of his hind legs. Every time he took a step, it bounced and jostled, an unusual feeling to the normally-slender Night Fury.

Eventually, as his tum rounded out, it lifted him off the ground, and he made a small growl in surprise at the interruption to his escape. It was around the same time that the rest of the pile of goo finally disappeared inside him. He swallowed hard a few times to make sure it was all down, and then burped.

He moved his legs to keep walking forward before remembering that he couldn’t quite reach the ground, his wobbling belly so swollen beneath him that his legs were pushed apart around the massive, bloated ball of jelly sitting in his gut. And he wriggled and strained to reach the ground and step forward, the sloshing of the goo kept his body squishing and jiggling without any progress.

After a moment, he took a break, panting. He made a rumbling noise and shook himself, causing another ripple through his squishy figure. He was vaguely aware of the rest of him growing softer and heavier as the slime began to digest, adding layers of fatty padding to his frame. Even when he was eventually able to touch the ground with his toes, though, he realized that moving would be too difficult for now, his body weighed down like a bowl of jello.

With nothing else to do, he yawned and decided to sleep. He wasn’t going to be going anywhere for a while. Even if he got to the entrance right now, how the heck was he supposed to fly? He might as well wait and relax a little, getting used to his new weight as his body digested the slime.

It was his day off, after all.