The most completely documented demon in the Western record, with a source trail running from scripture to Talmud to grimoire. In the Book of Tobit he is the demon who loved Sarah and killed her seven bridegrooms on their wedding nights, until young Tobias — coached by the archangel Raphael — burned the heart and liver of a fish on the bridal-chamber embers. The smoke drove Asmodeus 'to the uttermost parts of Egypt, where the angel bound him.' It is the oldest fully narrated exorcism in the Western canon, countermeasure included.
The Talmud gives him a stranger dignity: Ashmedai, king of demons, tricked and bound by Solomon with a ring bearing the Name, pressed into building the Temple, and full of unexpected moral lessons. The grimoires inherit the king: Goetia #32 shows three heads — bull, man, ram — a serpent's tail, goose feet, and a mount of infernal dragon.
Binsfeld's classification (1589) assigns him lust among the seven princes of sin. The Goetia adds a procedural note the archive enjoys: the operator must stand bareheaded before him, or he will deceive.