'Again and again, no matter how I lay them out - ... - the lightning-struck tower ... Calamity. Disaster. Coming nearer all the time ...'
-- Sybill Trelawney (HBP25)
A special deck of cards used over the centuries for Divination. The “Lightning-Struck Tower” was the card Sybill Trelawney kept seeing over and over just before Dumbledore’s death on top of the Astronomy Tower (HBP25). This can be counted as one of Trelawney’s actual prophecies.
The proper name for the card is “The Falling Tower,” and it shows several people falling, just as Dumbledore fell to his death, as well as Snape figuratively “falling” from grace in Harry’s eyes and losing the respect and trust of the Order of the Phoenix.
Another card mentioned by name is "The Hanged Man" which is the name of a pub in Little Hangleton, near the Riddle House where Voldemort killed his family and the caretaker, Frank Bryce (GF1). The image of someone suspended upside down is reflected in the spell Levicorpus, used by the Death Eaters on a Muggle family at the Quidditch World Cup (GF9), and seen in "Snape's Worst Memory" of James Potter using the spell to de-pants him in front of his classmates (OP28). In many ways, Harry is also the "Hanged Man" who can't escape his fate according to the Prophecy that he must keep facing the Dark Lord again and again.
1590s, from French tarot (16c.), from Old Italian tarocchi (plural)- cards used for fortune-telling