Not to be mistaken with the similarly named Alp-luachra, the alp is sometimes likened to a vampire, but its behavior is more akin to that of the incubus. It is unique from both of these creatures in that it wears a magic hat called a Tarnkappe, from which it draws its powers. The word "alp" is a variation on the word "elf". It is also known by the following names: trud, mar, mart, mahr, schrat, and walrider. Many variations of the creature exist in surrounding European areas, such as the Druden and Schratteli, or Old Hag in English-speaking countries.
An alp is typically male, while the mara and mart appear to be more feminine versions of the same creature. Its victims are often females, whom it attacks during the night, controlling their dreams and creating horrible nightmares (hence the German word Alptraum ("elf dream"), meaning a nightmare). An alp attack is called an Alpdruck, or often Alpdrücke, which means "elf pressure". Alpdruck is when an alp sits astride a sleeper's chest and becomes heavier until the crushing weight awakens the terrified and breathless dreamer. The victim awakes unable to move under the alp's weight. This may have been an early explanation for sleep apnea and sleep paralysis, as well as night terrors. It may also include lucid dreams.
Sexual attacks by the alp are rare.
The alp is often associated with vampires because it will drink blood from the nipples of men and young children, though women are the preferred victim of the invariably male alp, for it favors the taste of breast milk.
Alps also exhibit a tendency for mischief similar to elves, like souring milk and re-diapering a baby; a maid must sign a cross on the diaper or the alp will put the soiled diaper back on her child. They also enjoy tangling hair into "elfknots" or chewing and twisting horse's tails. They will ride a horse to exhaustion during the night and may sometimes crush smaller farm animals such as geese to death during a pressing attack. Alps are also similarly blamed for minor illnesses and milking cows dry, for they enjoy the taste of cow's milk as well.
The alp is best known for its shapeshifting abilities, similar to the creatures from werewolf lore. It may change into a cat, pig, dog, snake or a small white butterfly. It has also been said that it can fly like a bird and ride a horse. The alp always wears a hat, giving it an almost comical appearance. The hat is known as a Tarnkappe (the literal translation being "camouflage cap" or "cap of concealment") which is simply a hat (or less commonly a veil) that gives the alp magic powers and the ability to turn invisible while worn (see also cloak of invisibility). The hat is visible no matter what shape the alp takes. An alp who has lost this hat will offer a great reward for its safe return. The alp also possesses an "evil eye" whose gaze will inflict illness and misfortune. Removing or damaging this eye also removes the alp's malicious intentions.
Protections against an alp include laying a broomstick under a pillow, iron horseshoes hung from the bedpost, placing shoes against the bed with the toes pointing toward the door, or placing a mirror on the chest. Steel and crosses are also used. If awoken by the alp and finding him still there, one can address him by asking him to return in the morning to borrow something or have coffee. The alp will dash away at once, arriving in the morning either in his "true" form, or else in the form of a human with eyebrows that meet to receive his gifts. The creature can be convinced to leave the victim alone at this time, but the alp will beg pitifully and at length not to be turned away. Plugging up any holes, specifically keyholes, before a visitation will keep the alp out. Plugging them during a visitation will invariably seal it inside the room, as they can leave only through their original entrance. A light kept constantly on during the night will also effectively ward off an alp. A sentry may also be employed to wait and watch for the alp to attack the helpless sleeper, the alp may be driven away if caught by someone not under the alp's influence. Similar to the German Neuntoter, alps are weakened or immobilized by shoving a lemon in its mouth should it be caught resting during the day. The alp appears all but impossible to kill, and sometimes even after being turned away it may reappear years later in a worse mood.
The alp's history originated in the mountainous regions of Germany and Austria. The alp's Tarnkappe, as well as its demeanor and abilities, suggest that the dwarf king Alberich from the Teutonic epic poem Nibelungenlied is the source of inspiration for much of the alp's mythology. In Teutonic myth and folklore, alps were considered friendly elf-like beings which lived in the mountains, but eventually turned more negative and malevolent. The characteristic magic that the alps possess also bear the creature much resemblance to the Kobold, particularly Hodekin.
The alp, in many cases, is considered a demon, but there have been some instances in which the alp is created from the spirits of recently dead relatives, more akin to a spirit or ghost. Children may become an alp if a woman bites a horse collar to ease the pain during an extremely long and tortuous childbirth. Also, a child born with a caul or hair on the palms may become an alp. If a woman who is pregnant is frightened by an animal, the child may be born an alp. Stillborn infants are also suspected to return from the grave as alps and torment their family. People who have eyebrows that meet are suspected to be alps. As with the case of werewolves, sometimes a normal human or animal may become an alp during the night. They are typically unaware of their nocturnal activities and are invariably in disguise while doing so. Finding an alp while it is not active simply requires injuring or otherwise marking it during one of its attacks, and seeking out the being with a similar mark during the day. The person can then be cured if it is found out who sent them the curse, or how they became cursed to begin with. Witchcraft is often the prime suspect in this case.
Sometimes an alp is a spirit summoned by a witch or an evil person wishing harm on another, and sent to torment them. Tricking an alp may lead a person to its master. It may also have been expelled by the breath of the horerczy, a German demon which exhales vampiric butterflies.