Tarot cards have a centuries-long history in use for fortune-telling and other forms of divination. A deck consists of twenty-two Major Arcana (numbered 0 through 21, each with a distinctive name and image) and fourteen cards (King, Queen, Knight, Page, and 1 through 10) of each of the four suits wands, cups, swords, and pentacles. Similar symbology is found in pagan religions.
The best-known of the many competing designs of tarot decks is that devised by Arthur Edward Waite, commonly called the Rider-Waite deck after its official publisher (the illustrations were done by Pamela Colman Smith). Waite, who also wrote the accompanying Pictorial Key to the Tarot, was a bitter rival of Aleister Crowley, who is considered an important figure in Bree's religion.
In the "swimming drop" from Cassieiswatching a tarot card was found. Following the find there was a "denounciation" on the Cassieiswatching YouTube page for the video. If the card was switched the used of a tarot card may point to a Lonelygirl15 fan (because of the Crowley connection), but it could also have been random coincidence.