Silvermist

Silvermist are white cloud-like structures made entirely out of nanites. Formed from some ancient experiment gone wrong, these angelic clouds consume ships,entire planets and other void creatures. During the Ancient Age, they were considered a menace to colonies as they would devastate them by eating all organic life it comes in contact with. As they comsume, they grow larger and larger they're even known to eat the missiles sent to destroy them. Only ion weapons are known to affect them.