In ancient Greece, Tyche (also spelled Tykhe) was the goddess of luck, chance, providence, and fate. Her name is the Greek word for luck. In Rome, her equivalent would have been the goddess Fortuna.
Each city after a while developed their own iconic version of Tyche. Many considered her to be blind, so she appeared blind in statues or drawings. Others gave her a mural crown (a crown like the walls of a city). Most of the time she appeared as a younger middle-aged woman in typical Grecian fashion for women, sometimes seated, sometimes standing, etc. Tyche was also seen to hold a rudder, indicative of her ability to guide the affairs of the world. She was also shown holding a ball, representing the unsteadiness of fortune. Often she was shown with Nemesis, who was cautiously considered to be Tyche’s negative side.
Tyche was more than a simple goddess of luck. She was more than the goddess a person could appeal to for good luck–she was also the goddess that governed the fortunes and prosperity of a city. This elevates her to the status of Important Goddess, though strangely there are few myths about her. When she was in her aspect of guiding the affairs of the world, she was included among the Moirai, or Fates. The people of the city could appeal to her not only for their personal fortunes but also for the protection and prosperity of the city, which was important as not all cities had a patron god or goddess to appeal to in the manner that Athens had Athena.
Her genealogy varies; some authors say she is a daughter of Zeus, or Oceanus and Tethys, or Hermes and Aphrodite, etc. A major temple of hers was in Hellenistic Egypt, in the city of Alexandria, and was called the Tychaeon. It was purported to be one of the most magnificent temples in the Hellenistic world (probably because of her status as a goddess of luck–the better her temple, the more good luck she might give out).
Tyche was considered to be a fickle and capricious deity. She could give her good fortunes for a while, but just as easily withdraw them on a whim. This means that while she may have been a cherished deity at some times, during others she was reviled.
Light and Dark Sides
On the positive side, Tyche could help people. However, her help was fickle, and this is part of her Dark side. She was considered a whimsical goddess, which considering her duties with luck and fate, this makes sense. There likely was no maliciousness when she withdrew her favor–if there were, it probably would have shown up in a myth somewhere, as things of that nature tend to be popular in myths. Tyche is a middling goddess in a gray area–she helps people by granting her favor, but she also withdraws her favor on a whim and can cause the downfall of an individual’s fortunes or the downfall of an entire city or empire.