Sigma is capable of projecting a face over his...skull features. Usually to drop some of that intimidation look, most like during meetings or speeches, or a 1 to 1 conversation with a friend. Capable of facial expression.

I'm just uncertain between having it being like...some sort of physical projection capable of being touched, or be felt. Either by hard light or some sort of ferrofluid that hardens up a bit to feel like skin once former properly over his visage.

Again, by Anteroga. teethtoflesh on twitter.