The Triquetra and Charmed
Throughout the show the most prominent symbol that is displayed it the triquetra. This symbol is located on the Charmed Ones Book of Shadows and is a powerful symbol for the Power of Three, meaning the three Halliwell sisters.
The triquetra is used on the Book of Shadows as a religious symbol, because it is the mark of the Charmed Coven. It is the symbol that identifies the Charmed witches, and is found in various places, such as the Book of Shadows (see picture to the right and bottom right), on the blanket that covers Piper Halliwell's baby Wyatt (see picture to the right), and even the collar of the sister's cat Kit who is present in the first three seasons of the show (see the picture on the bottom left).
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Besides a symbol of their identity as witches, the triquetra also is used as a symbol of the relationship between the sisters. During the seventh episode in Season Three, "Power Outage", the sisters end up in a huge fight due to demonic influence and use their powers on each other. This lack of sisterly relationship causes the sisters to lose their powers and breaks the triqutra apart. As seen in the video below, the sisters are able to restore their bond and therefore restore the triqutra.
