Tyche is the Greek goddess of luck and chance, whose Roman counterpart is Fortuna. She was sometimes regarded as a fourth Fate, but not legitimately so, as she is not recognised as a fate, though she is in a way intertwined with fate. She is commonly represented with the Cornucopia and the wheel of chance.
The daughter of Oceanus and Tethys, Tyche is one of the three thousand Oceanids. In ancient times, Tyche was worshiped as the deity who presided over city and individual prosperity. While Tyche is known for giving people good luck, she is sometimes opposed by Nemesis, the goddess of balance. If a person receives too much good luck, Nemesis will provide them with bad luck to cancel it out.
- Tyche's cabin at Camp Half-Blood is Cabin 19.
- According to Rick Riordan's website, Tyche is the most difficult goddess to find. It is said that if you just keep on praying for good luck, she is not as likely to give you some, and that if you just go ahead and do something, chances are she may lend you some. This explains the random behavior of her children.
- Sometimes the Constellation Virgo is associated with her.
- On Rick Riordan's website, Nemesis is said to be sisters with Tyche's Roman counterpart, Fortuna. Whether this is true to the series or if Rick Riordan made a mistake is unknown.
- Tychokinesis, the ability to manipulate probability, is named after her.
- In the books, Tyche is seen only to bring good luck, but in mythology, she can grant either good or bad luck.