'"It had a spell put on it by an old fakir," said the sergeant-major, "a very holy man. He wanted to show that fate ruled people's lives, and that those who interfered with it did so to their sorrow."
As per the novel, with Wikipedia saying its a talisman that grants its possessor three wishes, but the wishes come with an enormous price for interfering with fate. But I have no doubt that the players will avoid this trap, because they're smart enough to be wary of anything that pops up in my game. They already seal a Aswang spirit away that trapped inside Charlie Sheen (giving the idea why he had tiger blood). I had thought at least one pc would put the spirit to use, but I guess having a spirit in your employment that eats unborn babies was a little too much even for him.
But a small group of folks who want to be werewolves and vampires getting such a talisman, now that could only be fun! I want these guys be like the small group Harry met in the novels that were mad at him for preventing their curse, and smoke bombed his home. Role-playing pains-in-the-ass but not really bad kids who got sucked into the large battle that's about to happen in the city.
So cross your fingers for Adolph Lowell, Raven Morgoth, Belinda Tilenis, Lovecharm, Autumn Brimstone, Hope Devonshire, Lanius Nicodemeus, and their Prince and owner of the paw, Julian Night that everything doesn't go straight to chaos once he makes the first wish. But I should mention that there aren't any established vamp courts in the city, since one of the aspects of the city is 'Flotsam & Jetsam'.