The Sword / Dagger is one of the magical weapons, or elemental tools, of Western ceremonial magic, the set of implements the magician consecrates and uses in ritual. It stands for the intellect and the analytic, dividing power; it is used to define, banish and cut.
Tool and element
In the four-fold scheme it is attributed to the element of Air. The four elemental weapons, Wand, Cup, Sword and Pentacle, correspond to the four suits of the tarot's Minor Arcana and to the four points of the ritual circle, a scheme drawn together in the Hermetic Order of the Golden Dawn from 1888 out of older Solomonic and grimoire material.
An older, better documented tool
Edged instruments have a clearer grimoire pedigree than the other three weapons: the Key of Solomon describes several distinct knives and blades, including ones with differently coloured hilts reserved for different operations, each with its own timing, materials and consecration, well before the Golden Dawn's 1888 systematization folded a single sword into the fourfold elemental set; S. L. MacGregor Mathers, credited with compiling that set, had translated and published an English edition of the Key of Solomon in 1889. The black-handled ritual knife of later Wiccan practice, the athame, is thought by some scholars to trace its unusual name through a chain of manuscript and print corruption back to the Latin artavus, a small knife, in earlier grimoire copies. As with the Wand, the Air attribution used here is the Golden Dawn's own and is not universal; some earlier strands assign the Sword to Fire and the Wand to Air instead. The weapon is described here as an element of that documented tradition of ceremonial magic, a body of practice studied historically rather than endorsed.
Sources The Magicians of the Golden Dawn: A Documentary History of a Magical Order 1887-1923Ellic Howe with Grimoires: A History of Magic BooksOwen Davies