The Tyet, Knot of Isis is a distinctive type of amulet that was fashioned in ancient Egypt. It's purpose was protective and it was typically made of carnelian, red jasper or faience, but was sometimes carved from other materials such as lapis lazuli.

According to Egyptian Mythology, the god Osiris battled with his brother Set for dominion over the world. Set triumphed, and having done so, dismembered the body of Osiris and scattered the pieces over Egypt. Isis, the sister-wife of Osiris, wept tears of blood, upon hearing of Osiris' death. Isis then caused these tears to be transformed into the crystal known as carnelian, a very
hard reddish-colored stone. Isis then shaped the crystallized tears into an amulet - the one now known as a Tet (sometimes written as Tyet or Tit).

Isis had the pieces of Osiris' body reassembled, and briefly re-incarnated her brother-husband, long enough to conceive their son Horus, who went onto conquer and banish Set.

Osiris was then sent into the underworld, or "Tuat," where he became the Prince of the Afterlife. To protect Osiris on his journey, Isis placed the Tet amulet upon the neck of her beloved,
spoke some words of magic over the Tet, and sent Osiris on his way.

The translated Chapter of A Tet of Carnelian, in the Papyrus of Ani (or as it is better known: The Egyptian Book of The Dead.) reads thus:

"The blood of Isis, the spells of Isis, the magical words of Isis shall keep this great (or shining)
one strong, and shall protect him from whosoever would harm himdo to him such things as he abominateth."

Some portion or all of this passage would typically have been inscribed via hieroglyphic symbols onto the amulet.

The Tet of Carnelian is also referred to in various manuscripts as the Knot of Isis, Buckle of Isis, Girdle of Isis or Tie of Isis. Although the glyph and the amulet themselves appear to be in what some people believe to be the form of a man, most Egyptologists believe that the form actually represents the female reproductive organs, i.e.- the vulvavagina of Isis.In ancient Egypt the Tet amulet was considered to be a strong protective influence against evil, misfortune and bodily harm.