This male demon appears in the nightmares of men, women, and children, and in the old days, people believed alps caused sleeping problems, such as sleep apnea, sleep paralysis, and sleep walking. Unfortunately, it only resides in dreams, making it almost impossible to kill.
In the period before about 1000, the Old High German word alp is attested only in a small number of glosses. It is defined by the "Althochdeutsches Wörterbuch" as a "nature-god or nature-demon, equated with the Fauns of Classical mythology ... regarded as eerie, ferocious beings ... As the mare he messes around with women". Accordingly, the German word "Alptraum" (literally "elf-oppression") means "nightmare". There is also evidence associating elves with illness, specifically epilepsy.
In a similar vein, elves are in Middle High German most often associated with deceiving or bewildering people "in a phrase that occurs so often it would appear to be proverbial: 'die elben/der alp trieget mich' (the elves/elf is/are deceiving me)". The same pattern holds in Early Modern German. This deception sometimes shows the seductive side apparent in English and Scandinavian material: most famously, the early thirteenth-century Heinrich von Morungen's fifth Minnesang begins "Von den elben virt entsehen vil manic man / Sô bin ich von grôzer lieber entsên" ("full many a man is bewitched by elves / thus I too am bewitched by great love"). Elbe was also used in this period to translate words for nymphs.
In later medieval prayers, Elves appear to be threatening, even demonic, force. Evidence includes Latin prayers found inscribed in lead amulets from southern Scandinavia and Schleswig. The most famous is the fourteenth-century "Münchener Nachtsegen", a prayer to be said at night.
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, Alpe 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.