Harry Potter and the Prince of Slytherin

"Are you really sure?" Hermione asked nervously for the fifth time.

"Yup!" Draco said, "As long as you keep the suitcase open and be prepared in case of emergencies, I'll be fine."

Hermione sighed and nodded, "Good luck!"

Draco chanted a spell pointing at himself, as he created a bubble around his face. Draco looked back at Hermione one last time and with the Bridle, in his hand, he jumped inside the well. With the Bubble-Head Charm breathing underwater was extremely easy. Diving in he looked around to find nothing, he kept his senses up as he kept swimming when suddenly he felt something move deeper inside the well.

"Sigh! They really must be planning on killing me, huh!" Draco said snorting as he chanted, "Lumos Maxima."

Draco's wand grew very bright, as he started swimming deeper. The deeper he went the wider the well got and before he reached the end of the well, he was already deep inside a what looked like a water castle. There were pillars and broken statutes all over the place. His eyes fell on the darker area only to realize that the place kept going deeper.

"What is this place?" Draco muttered not expecting there to be such a thing inside the well. The place reminded him of the many secret rooms in Hogwarts. "I wonder how many more are there?" Draco pondered when suddenly at the corner of his eyes, Draco saw something move behind one of the huge pillars but before he turned over, the thing had already disappeared. Draco carefully looked around those pillars one by one, his breathing getting a bit heavy.

Draco tried to calm down and feel the movement around him. Fighting underwater was very different from what he had expected, the limit in his movement caused him to slow down and his efficiency dropped down a lot as well. Draco felt something behind him as he quickly turned around to find a horse-shaped creature coming towards him at a full speed.

"Not so quick!" Draco snorted as he quickly used a stunning spell at the horse which it managed to dodge easily. Draco seeing the kelpie dodging wasn't nervous at all instead, he was smiling. Without any delay, Draco quickly used the placement charm shifting the bridle from his hand to the horse's mouth.

The horse tried to shook the bridle off of it but failed as it started transforming into something else, a Scottish loch. Draco smile soon faded away as the kelpie who had just transformed was too close to him. Draco tried to dodge but the kelpie got hold of him and with him holding on, the kelpie started diving in towards the deeper part uncontrollably trying to shake the bridle off of it.

Draco who barely managed to dodge grabbed on the Kelpie's hair as the kelpie kept diving deeper and deeper into what seemed like an endless pit. Getting a hold of things Draco looked around to finally find the reins attached to the bridle. Taking his chances Draco quickly grabbed on the reins and using it, he climbed on the back of the Kelpie and pulled back.

The kelpie who kept struggling as it kept diving felt something on it's back but before it could do anything it had to forcefully stop as Draco kept pulling its head back with the rein. It struggled again and again but Draco didn't let go. After not being able to do anything it let out a cry.

Draco felt the Kelpie giving up, as he relaxed until out of nowhere another Kelpie came towards him, pushing him off the back, Draco knowing the situation wasn't in his favor anymore quickly used an explosion spell, pointing at what seemed like a statue blowing it away. The statue broke off and started sinking and without thinking anything Draco held on to it, sinking deeper and deeper as the kelpies kept chasing him.

After what felt like an eternity, The statue landed on the floor crashing. Draco used a protection spell to get off but the impact still managed to get to him, as he was thrown a bit far away. Trying to swim a bit he used a spell again making the place brighter.

He swam around the place finding a couple of dead Kelpies around the floor, the bodies still looked a bit fresh so he figured the toxicity of the potion had caused them to die. The place was more like a small hall and wasn't as big and wide as Draco expected it to be. He looked around for a while only to realize that he was surrounded by four huge statues when he looked up.

"The founders?" Draco said to himself as he looked around carefully. Draco was certain that they were the founders as he had seen them in a couple of books he had read and Hogwarts literally had their statues and paintings all over the place, especially the entrance which contained giant statues of the founders. But among the four only one of them caught the eye of Draco, the statue of Rowena Ravenclaw. The statue was very similar to the others but the thing that caught Draco's eye was the diadem on her head which had a huge pearl on top of it, unlike the other statues which were made of stone, the pearl seemed real as it still shined brightly and the condition down here hadn't even affected it. Draco wanted to swim closer to inspect it but his eyes quickly turned towards the two kelpies who were swimming furiously towards him.

Trying to prepare for battle he looked around, to find something unusual on the ground. It was a small nest filled with eggs, Draco was now clear as to why both of these kelpies were so hostile against him being there and it not wanting to obey Draco. Draco snickered as he quickly pulled the whole nest towards him. "Accio."

The nest flew over to Draco's hand. There were 7 eggs in the whole nest which barely fit into his arms.

Seeing its eggs being taken the Kelpie's let out a weird noise, moving quickly. Knowing his job was done here, Draco smiled and pointed his wand up. The two kelpies came closer and prepared to attack him from two sides. Just as they were about to get close to him, Draco chanted, "Ascendio."

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Outside Hermione was getting worried about Draco as it had already been a half an hour since he was gone. She was already thinking of calling Hagrid or a professor to help when out of nowhere, Draco came flying out of the well, quickly jumping inside the suitcase and soon two huge creatures jumped out of the well as well and followed him inside the suitcase.

All this happened so quick, that Hermione barely had enough time to react. After coming to her senses she looked around and pondered for a while, as she hesitantly jumped inside the suitcase as well.

Inside Draco quickly placed the landing location into another lake he had created the day before and dived into it again. The air in his bubble mask was running out due to all the fiasco and it was getting harder and harder to breathe. Seeing the Kelpie following him, Draco smiled as he put the nest, gently on the ground in front of the Kelpies and slowly backed away.

The kelpies swam near their eggs, checking on them to see if they were okay. One of the kelpies which Draco figured was the male looked at Draco with hostility. Draco stayed calm and stayed where he was. He wanted Kelpies to like him and not hate him since they were basically going to live with him now and he needed them.

Draco had already made up his mind on using these beasts to help him on his quest, so he had already planned on collecting several of them, the kelpies being one of the very few. The Kelpies were very useful, especially in water. Draco didn't think that he would ever have to fight underwater but in case he did, Kelpies were the best choice to help him assist in it. It's incredible speed and shape-shifting power made it be one of the best assistance in underwater fights. Draco knew if he managed to control and train these Kelpies properly, he could create a good fighting strategy underwater.

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I don't know how Kelpies reproduce and neither was it mentioned in the wiki page so for convenience sake, let's just pretend it lays eggs.

Ascendio = https://harrypotter.fandom.com/wiki/Ascendio

If you don't know what the spell is.