Once you have the output rendered. You can use that rendered sequence as a mask.

75% of original size (was 667x19) - Click to enlarge

Simplified:
The idea is that factor is the mask of how you want two shaders to blend.   One shader being the all the related nodes that make up the cc3 head and another shader being anything you want(black, purple, glowing blue, shiny metal, anything), so those two get plugged in.   Then the (fac) factor will be the vines sequence which says, all the black will be one shader and all the white will be the other shader. You could swap it around so it looks like skin is being created around his face.   You could have it as a transparent material and the face is being created from the vines(hrmm I should actually try that).

anyways I hope this helps clarify a bit more.