A Runed Ruby is an enchanting crystal that can be used on an enchanted forge on any enchantable item. This gem will modify any weapon to deal fire damage in addition to physical damage on a successful hit, as well as modify any armor to have a 5% increase in fire resistance.
This item was introduced in Geneforge 3 and has stayed in the game ever since. The value of a Runed Ruby is 400 coins yet since the sale price is 1/8th of the value, merchants will buy the item for 50 coins. Often, people accidentally confuse the Runed Ruby with the Runed Amethyst. This is because of the similar name and icon.