Kelpie

• Type: Magical Beast
• Ministry of Magic Classification: XXXX (Dangerous)
• Native to: Great Britain and Ireland
• Habitat: Rivers and lochs

A Kelpie is a shape-shifting water demon native to the lakes and rivers of Britain and Ireland. While it can take on many forms, it most frequently appears as a horse with a mane composed of bulrushes. This equine form is a deceptive tactic to entice unwary humans to mount it. The world's largest and most famous Kelpie, the Loch Ness Monster, prefers the form of a giant sea serpent. In its aquatic environment, a Kelpie is described as immensely strong and dangerous. Its primary goal is to drown and consume its victims.

The Kelpie's primary magical ability is shape-shifting, which it uses for predation. By appearing as a harmless-looking pony or a beautiful human, it lures victims, particularly children, towards the water. Once a rider has mounted its back, the Kelpie's skin becomes adhesive, trapping the victim as the creature dives to the bottom of the lake or river to devour them. It characteristically leaves the victim's entrails to float to the surface. Despite its ferocity, a Kelpie has a specific weakness. Placing a bridle, enchanted with a Placement Charm, over the Kelpie's head will render it docile and harmless, subjecting it to the will of the wizard who bridled it.

Kelpies are a well-documented magical species, classified as XXXX by the Ministry of Magic in the textbook Fantastic Beasts and Where to Find Them, indicating they are dangerous and require specialist knowledge to handle. The Loch Ness Monster is the most famous individual Kelpie. It has successfully avoided Muggle capture for centuries by continuously shifting its form when sighted, remaining one of the most intriguing subjects in the field of Magical Creatures. At least one Kelpie is known to inhabit the Black Lake on the grounds of Hogwarts School of Witchcraft and Wizardry. In Harry's sixth year, Potions Master Horace Slughorn expressed a desire to acquire Kelpie hair from the lake for use in his potions, but noted that the Headmaster would not permit it. This creature was also alluded to in Harry's second year, when he incorrectly guessed that Gilderoy Lockhart's secret ambition was to “get rid of the Kelpie in the Black Lake” on a D.A.D.A. quiz.

The Kelpie serves primarily as a world-building element, illustrating the diversity and inherent dangers of the magical world that exist just beyond Muggle perception. Its inclusion in Fantastic Beasts and Where to Find Them and as a topic in Hogwarts classes establishes it as a known threat within the wizarding community. The revelation that the Loch Ness Monster is a Kelpie provides a concrete example of how the magical world explains phenomena from the non-magical world. Furthermore, the confirmation of a Kelpie in the Black Lake by Horace Slughorn reinforces the peril of the Hogwarts grounds, even in areas students frequent.

The Kelpie of the Harry Potter universe is directly based on the mythological creature of the same name from Scottish folklore, a malevolent water spirit said to haunt lochs and rivers. In the film Fantastic Beasts: The Crimes of Grindelwald, Newt Scamander is shown to keep a large, powerful Kelpie in his basement menagerie. It is depicted as a massive, powerful creature made of flowing, green, kelp-like tendrils. Newt demonstrates the canonical method for subduing it by using a bridle, which instantly renders it calm and rideable (film).