The Athame, pronounced "a-tha-may" or "a-tha-me", a.k.a. "the black-handled knife", is a magical dagger and one of the four principle tools used by witches and magicians of many traditions, but especially Wicca, Neopaganism, Satanism and Ceremonial Magic. The athame first appears in writing in the Key of Solomon where it is referred to as the 'arthame'. For an image of an athame, click HERE.
Traditionally, the athame is a double-edge, black handled knife. Additionally the athame may have a magnetic blade and have it's handle engraved with various magical symbols. The athame must never be used to cut anything or to harm anything, be it animal or human. The athame must never be used for any trivial purpose and should only be used for it's role for inscribing the magical circle by holding it in the air and walking around in a circle as well as an aid to summon and control deities or spirits.The athame may also be used by plunging it into the ground or into the chalice, another tool of the witch, in a specialized ritual referred to as 'the great rite' which takes place on or near May 1st. The athame in a coven setting, is also sometimes used in a mock threat of harm by witches entering the sacred space for ritual. During such instances the tip of the athame blade is placed over the witch's heart and a phrase similar to, "It is better that you should rush upon this blade than to enter this circle with fear in your heart. How do you enter?", is spoken. The witch responds by saying, "In perfect love and in perfect trust". In such instance no true threat of harm takes place as the individual is made aware of what will take place.
As with most magical tools, the athame must never be touched by non-witches and preferably by no one other than the owner or at least fellow members of the coven or circle. If the athame is touched by a non-witch or someone other than the owner then the blade must be ritually cleansed and blessed before it can be used once more in ritual.
*Note: I'm told that Satanists will use the athame to direct black magic against an enemy. If this is true then this would be an example of someone using the athame to harm another, but this would be a practice found among Satanists and would still represent a "magical use" vs. a mundane use.