Board Thread:Game Discussion/@comment-174.28.112.47-20131008045122/@comment-23825938-20131008110615

Earth/Spirit + Water/Air =  Earth/Water  OR  Earth/Air  OR  Spirit/Water  OR  Spirit/Air.

Moontide is Spirit/Water so you CAN get it, but it's still only a very small chance...

If these are two of your better armors I say don't fuse them. But if you don't use them, you can always go for it.