Harry Potter woke up and groaned, looking around muzzily. The last thing he remembered was seeing a dark, hunched figure crouched over a pale shape, clearly consuming something from it, then he had blacked out, being only vaguely aware as Fang had taken off at top speed, barking and howling at the top of his lungs as he did so.
Once he was fully conscious again, Harry became aware of something holding him with a firm grip, and he fought to get free upon seeing that it was a spider, only ceasing his struggles when he also saw that he was very high up in a tree.
"Relax, little one," a voice said softly in the boy's ear. "I will bring no harm to the one who represents the last best hope I have of saving my kind."
"What do you mean?" Harry asked, only now realising that he was, for some strange reason, completely naked.
The creature set Harry securely on a branch and backed off a little until the eleven-year-old wizard could see that it looked like a spider with a human torso where its head should be.
"Why am I here?" the boy asked in a quavering voice.
"Because my mate has left me heavy with her eggs, and the time has come when I must mix them with my seed as I inject them into a host. Since the other has not come despite his promise, I have chosen you in his stead."
"Who was supposed to be in my place?" Harry couldn't help asking curiously.
"I only know him as a large male with lots of hair and the scent of many creatures."
"Oh, that sounds like Hagrid. But wait, how are you going to put the eggs inside me?"
"I will place my reproductive organ inside the hole at your back and inject it full of the eggs with my seed mixed in with them."
"You can't! I need that to use the toilet."
"Such strange phrases you humans use to describe the passing of waste. Nevertheless, that is what I need to use, so I have already made the appropriate adjustments," the creature stated, gesturing broadly at his captive.
Because of the gesture, Harry couldn't help looking down at himself, only to see an orifice on his abdomen. So, deciding that enough was enough, he began to climb from the tree he was in. He had not got more than a couple of handholds downwards, however, when the spider creature recaptured him, set him back on the branch, then secured him face down on it with sticky silken cords.
"Now," the creature began, "the hole I gave you will allow you to pass waste, although you will require more fluids than is usual for your kind while it exists. Now that I have explained this, it is time for me to empty your body of waste."
Harry tried to resist the probing of his virgin sphincter, but years of deliberate undernourishment by his caregivers had taken their toll on the strength of his muscles, and they soon gave way to the moist tube that snaked inside him. First the tube filled him with a warm fluid, which was held in place for many minutes before the resulting slurry was sucked out, then it moved further inwards and repeated the process over and over until the end of Harry's large intestine was reached.
"This is why we have to do this with humans," the creature stated. "Human scat is the only type that is nourishing to us."
"Scat?" Harry was thoroughly bewildered by now.
"That is another word you humans use for waste. Now that I've emptied you out with my digestive enzymes, it's time to fill you up again."
With that, something not as long as the tube was inserted into Harry's anus, entering easily despite its greater girth, and the boy found himself hard as though he badly needed to urinate except that he had no strong sense of urgency, then he felt lots of small lumps with a thick liquid blended amongst them being forced inside of him. The young wizard orgasmed dryly many times over the next several minutes, then the spider creature withdrew its organ before sealing Harry's anus closed with some strong webbing.
"This is why I would have preferred to lay our eggs inside the Hagrid-man. He has more space within him, so his abdomen would not have grown so large."
Harry looked down at his belly for a second time, his horror knowing no bounds when he saw that it was so large it made him look as if he was seven months pregnant, bulging out incongruously from his underweight frame and completely obscuring his immature package from view. He attempted to empty his extremely overfull rectum, only for this desire to be frustrated by the webbing between his buttocks.
The wizard started to cry as the shock of his violation caught up with him, and the spider creature unbound him and gathered him into his arms, murmuring, "Hush, little one. It is not so bad as all that."
It took some time for Harry's sobs to cease, then once they had, he asked, "Where are my clothes?"
"Clothes, little mate?"
Harry gave a shudder at that as he replied, "The items you removed from my body."
Without another word, the creature gathered his now pregnant mate into his arms again, using a webline to get them both safely to where he had left Harry's robes and wand under a tree. The boy dressed quickly, noticing that his underpants now fitted him, thus deciding to eschew his crude belt of twine for the first time in his young life. After that, his new mate escorted him safely out of the Forbidden Forest and up to Hogwarts Castle.
✱ ✱ ✱
"What do you mean, we can't remove the eggs from the boy!" Minerva McGonagall, Transfiguration professor, almost shrieked, losing her calm for the first time since Rubeus Hagrid, Keeper of Keys and Grounds at the school, had met her at the beginning of his own first year many decades before.
"Well, it's like this, yeh see, professor. The arachnotaur sealed 'em in there good an' proper, an' operatin' won' get 'em out either. Believe me, I've tried tha' before."
"So what can we do for young Mr. Potter?" Poppy Pomfrey, Hogwarts' resident mediwitch, enquired.
"All we can do is allow him to come to his time an' let the little ones hatch."
"And what about Mr. Potter's physical changes?" Professor McGonagall asked in her usual practical manner.
"Oh, they won' last," Hagrid stated. "Just a few weeks after the pregnancy ends, it'll be like nothin' ever happened to him."
"With the exception of Mr. Potter's mind. I feel it's safe to say that this wil have a lasting mental effect on him."
"Yeah, but Harry's a kid. The mind's tough as old boots at that age," Hagrid relied stubbornly.
"I think you've spent so much time around animals that you overestimate the strength of the human psyche, Hagrid," Professor McGonagall pointed out. "It can be a fragile thing at the best of times."
"I'm so sorry!" Hagrid burst out. "If I hadn' allowed Harry's detention ter drive my other duties from my mind, I would've been the one ter end up pregnant instead o' him!"
With that, Professor McGonagall escorted a tearful and guilt-stricken Hagrid from the infirmary as Madame Pomfrey went to check up on her patient.
✱ ✱ ✱
A few months later, Harry was failing miserably to find a comfortable position in which to do his homework, when he suddenly felt the webbing that enclosed his anus loosening slightly. He struggled to his feet, his grossly distended abdomen making this extremely difficult, then he waddled as fast as he was able down the stairs and through the portrait hole.
"Ooh, mpreg!" the Fat Lady carolled as she saw the hugely pregnant eleven-year-old. "You'll be famous in fanfiction circles, dear! You mark my words!"
Harry simply shook his head and carried on walking. The woman in the portrait had been saying the same thing to him ever since his belly had grown too large for concealment spells to work properly, and the young wizard supposed it was just evidence of how crazy she was. Finally, after what felt like hours, Harry reached Hagrid's hut and banged on its door.
"Hang on a minute!" the huge man shouted. "I'm in the middle o' washin'!"
"It can't wait, Hagrid!" Harry exclaimed. "The babies are ready to come out!"
"Those aren' babies waitin' ter come out o' yeh, Harry," Hagrid patiently explained as he opened the door. "They're eggs. They won' hatch till yeh've laid 'em."
Panicked thoughts raced through the younger wizard's mind at this, then he noticed something and his eyes widened as he stared at an orifice on Hagrid's belly that resembled his own temporary anus.
"Yep," the half-giant said proudly as he pulled on his shirt and coat. "Spidey came back ter me jus' last month. O' course, 'cause I'm a mite bigger than yeh are, I don' show straightaway."
"You call that creature 'Spidey'?" Harry asked, bemused.
"Well, everythin's got ter have a name, an' Spidey's what I call him. Now, let's get yeh inter the forest so yeh can lay yer eggs."
With that, Hagrid swept Harry into his arms before carrying him at a rapid pace into the dark trees of the Forbidden Forest.
"Where did Spidey mate with yeh, Harry?" Hagrid suddenly asked the boy in his arms. "Tha' will be the best place ter lay those eggs of yers, I'm thinkin'."
Harry looked around until he found a landmark he recognised, then guided the groundskeeper to the scene of his violation. A few minutes later and he was naked from the waist down, Hagrid rubbing the boy's enormous belly in an effort to ease his pain.
"If yeh need ter play with yerself ter make this easier on yeh," Hagrid suddenly stated in a gruff tone, "I'll understand."
If Harry hadn't known any better, he would have thought the half-giant holding him was a pervert, but he could sense the other's embarrassment and said nothing, simply grasping his small penis to see if the idea worked. Surprisingly enough, the masturbation was helpful and the first egg emerged after just a few more minutes, the laying getting progressively easier with the appearance of each two inch long cylindrical ovoid.
By the time the laying was over, a few hundred eggs lay between Harry's open thighs.
"No wonder I got so huge," he said exhaustedly, yawning as his eyes threatened to close. "Do you want me to help you when your time comes, Hagrid?"
"Only if yeh want ter, Harry," Hagrid replied as he watched each of Spidey's children hatching then immediately scurrying off into the trees in search of their first meals. "Yeh do know yeh'll have ter do this again, don' yeh?"
"What? Why, for Merlin's sake?"
"Didn' Dumbledore tell yeh? Turns out arachnotaurs mate fer life. Not jus' with those o' their own species, but with the human part o' their breedin' triad, too. The only thing tha' will separate yeh an' Spidey now is the death o' either one o' yeh."
Harry knew he would have to look up arachnotaurs in the library, but he also knew that he really wouldn't mind if what Hagrid said was true. Up until the time he had become too big and heavy to move easily, the young wizard had enjoyed the entire experience once he had overcome his initial fear and horror.
Under a tree a few feet away, an invisible Dumbledore rubbed his hands as he smiled in triumphant glee. His experiment had proven to be a resounding success, and with the Boy Who Lived, no less! Maybe he should now see if the arachnotaur would lay his eggs inside first year female students. After all, being girls, they were better equipped for pregnancy, and young Miss Weasley should look most attractive waddling around with an enormous belly.
And although none of the three wizards realised it, Spidey sat in another tree and watched blissfully as both of his human mates contentedly accepted their roles as brood surrogates. They really had been the last hope for the survival of his kind since he and his mate had arrived in this dark forest several seasons before. Humans were the only animals in this strange place that had the nutrients necessary for arachnotaur sperm production in their waste, and large numbers of offspring had been the happy result.