A Runed Onyx is an enchanting crystal that can be used on an enchanted forge on any enchantable item. This gem will modify any weapon to slow enemies down in addition to physical damage on a successful hit, as well as modify any armor to have a 5% increase in magic resistance.

This item was introduced in Geneforge 3 and has stayed in the game ever since. The icon is the same used in the Golden Crystal but has a different color.