Geralt starts the game with one moon rune. Later, they can be purchased from a number of merchants, including the mysterious merchant, Haggard or Thorak in Vergen, or Falas, the Incredible Lockhart or Polycarp of Rinde during Chapter III. To use a rune, Geralt simply drags it over to one of the rune slots on a suitable sword in the inventory panel. Moon runes can also be used to craft blue, red or yellow meteorite ore, though given that the price of a rune is significantly higher than that of a piece of ore, it seems a poor use of the rune.