“Combine Spirit Attire" lets you create "Mythical Gear" that has both the stats of “Commandment Gear” and “Chaos Gear” by synthesizing the two together.
Performing the synthesis requires the requisite gear, gear materials, and Zeni.
The pieces of gear must be of the same type.
(Weapons must also be the same kind of weapon.)
Synthesis will not actually consume the pieces of gear, but their Spirit Attire stats will be removed.