In LOTR with Harry Potter system

"Protego!"

Sylas was prepared. The moment he tossed in the porcupine quills, he instantly cast a protective barrier around the cauldron, shielding himself and the workbench from the potion's volatile splash.

Only after the mixture calmed did he conjure a thick glass vial and magically siphon the bubbling green liquid into it, storing the corrosive substance with practiced ease.

The iron cauldron, however, was another matter. Its surface had been eaten away, melted into a twisted, blackened ruin. No Mending Charm could fix that.

But instead of being dismayed, Sylas grinned.

The Magical Drafts and Potions book had clearly warned: never add porcupine quills to a Boil-Cure Potion while the flame was still lit. Doing so would result in a disastrous chemical reaction, one potent enough to corrode through solid metal.

And Sylas had done it on purpose.

This failed potion couldn't heal boils, but it had turned into something even more valuable: an acidic green sludge, more powerful than any Muggle acid. One vial could burn through iron, bone, or even the sturdiest Goblin-forged locks. In the right hands, or the wrong ones, it was a weapon far deadlier than a simple spell.

Bilbo, who had been quietly observing the entire experiment, stared wide-eyed at the glowing vial from a safe distance.

"That... that's not something you plan to drink, is it?" he asked nervously, inching toward the door.

Sylas chuckled. "Definitely not. This one's for emergencies."

With that, he carefully sealed the vial, inscribed a rune of caution, and floated it into a reinforced lockbox.

Next, Sylas turned his attention to a more ambitious project: the Shrinking Solution.

A classic among witches and wizards, Shrinking Solution caused living beings to shrink rapidly, sometimes to the size of a walnut. It was useful for sneaking past guards, transporting livestock, or even escaping tight situations. On the flip side, it was also notoriously abused by thieves who shrank themselves to bypass magical wards and sneak into vaults or manors.

The ingredients for the Shrinking Solution were varied but familiar: Shrivelfig, daisy roots, dried caterpillars, wormwood, leeches, rat spleens, and most importantly, scurvy-grass essence.

Sylas had already prepared most of them, but the essence had to be made fresh.

He diced the scurvy-grass leaves, crushed them in a stone mortar, and transferred the mixture to his silver cauldron. A flick of his wand adjusted the heat as he stirred steadily, ensuring the extract was properly distilled. A steady stream of steam rose from the brew, filling the storeroom with a pungent, earthy aroma.

Once the reaction reached its peak, he murmured, "Finite Incantatem," and watched as the liquid neatly separated from the spent pulp. The pale residue at the bottom, soft, silvery-white, was exactly what he needed: concentrated scurvy-grass essence.

With that done, Sylas officially began making Shrinking Potion.

Shrinking Potion was a standard second-year subject at Hogwarts, but far more complex than the Boil-Cure Potion.

It required the precise addition of Shrivelfig, Daisy Roots, Caterpillars, Wormwood, Leeches, Rat Spleens, and Scurvy-grass Essence, all in specific quantities and carefully timed intervals.

The process was meticulous. Brewing took far longer than simpler potions and demanded far more focus.

Sylas began by preparing the Shrivelfig, squeezing out its juice while preserving the peel and pulp. He added the juice to a silver cauldron and let it simmer gently over low heat for twenty minutes. Next came the Daisy Roots and Caterpillars. Once added, the potion darkened to a thick green and began to boil. Sylas continued to simmer it down until its volume was halved, then extinguished the flame and left it to cool for thirty minutes.

When the time was up, he moved on to the next step.

Twenty-four drops of wormwood infusion, added one by one. After each drop, he stirred with his wand, alternating directions. Before adding the final drop, he stirred vigorously until a layer of foam formed across the top.

The bubbling potion now had to rest.

It would need twenty-four hours for the foam to vanish and the mixture to settle before the next steps could begin.

The following evening, precisely twenty-four hours later, Sylas resumed the process. He reheated the potion gently and added freshly prepared leech juice, stirring steadily and carefully as the potion began to lighten in color. When it reached a pale green hue, he introduced the final two ingredients: Rat Spleen and Scurvy-grass Essence.

This time, the cauldron required high heat, two full hours of boiling.

As time passed, the mixture thickened into a glossy, syrupy liquid of brilliant green. Sylas leaned over, scrutinizing the texture and color, then glanced at the potion book beside him.

"This looks right," he murmured, though a flicker of doubt remained in his voice.

But there was only one way to know.

Drawing a drop of the thick potion into a dropper, he squeezed it onto a carrot and marched outside with it in hand.

Bilbo, ever curious and ever suspicious, followed close behind.

Out in the garden of Bag End, a familiar sight awaited them: a rather dopey-looking pony nibbling on wild clover.

"Hey, Little Brownie!" Sylas called out, waving the carrot like a flag.

The pony, affectionately named Little Brownie due to its rich, chestnut-colored coat, perked up immediately. Gifted by the head of the Took family during Sylas's travels through Tookbank, it had been more of a companion than a mount. Since their return to Hobbiton, Bilbo had been the one diligently caring for the creature, even building it a modest but cozy stable out back.

Hearing Sylas's call, the pony's ears twitched. Catching sight of the carrot, its eyes gleamed with anticipation. It trotted over, tail swishing, and eagerly bit down on the offered treat.

Bilbo gasped and looked between Sylas and the pony, scandalized.

"Sylas! You're testing potions on poor little pony?"

Sylas rubbed the back of his neck sheepishly.

"There's only three of us here. I figured he was the best candidate. You wouldn't want me trying it on you, would you?"

Bilbo shot him a look that could have withered ivy. But Sylas's eyes remained fixed on the pony.

In just two seconds, the effects began.

A startled whinny rang out. "Neigh! Neigh!"

Before their eyes, Little Brownie began to shrink, his legs wobbling, eyes wide with panic as his surroundings loomed larger and larger.

From Sylas and Bilbo's perspective, the transformation was nothing short of magical. The pony, Little Brownie, was shrinking right before their eyes, its sturdy legs, bushy tail, and soft muzzle all compressing until it was no larger than a teacup. In the end, it looked like a handcrafted figurine brought to life, complete with a flicking tail and twitching ears.

Sylas gently scooped up the tiny creature in his palm. Little Brownie flailed his miniature legs in the air, snorting in confusion. Sylas examined him with fascination. "Looks like the potion worked perfectly. Just one drop got him this small. I wonder if a few more drops would turn him mouse-sized."

Bilbo stared at the pony, utterly stunned. Though he'd seen Sylas perform plenty of incredible magic, this was something else entirely. 

Seeing Bilbo frozen, Sylas chuckled and handed Little Brownie over. "Here, see for yourself."

Bilbo carefully cupped the miniature pony in his hands, feeling its warmth and weight. The realization hit him, this was real. His mouth opened, but it took a moment before the words came. "S-Sylas… is he going to stay like this forever?"

Sylas shook his head with a grin. "Of course not. Once the potion wears off, he'll return to normal. Just make sure he's on the ground when that happens, unless you fancy getting flattened like a pancake."

Alarmed, Bilbo quickly knelt and placed Little Brownie on the grass. He loved the creature dearly, but the idea of being accidentally crushed by it was not appealing.

Sure enough, about fifteen minutes later, Little Brownie began to tremble and glow faintly—then in a smooth puff of magical reversal, he re-expanded with a soft pop back to his original size.