Board Thread:Legitimate Canon Questions/@comment-190.27.47.99-20140313003832/@comment-4091815-20140313012303

Apparently cutting into the body is how the Nogitsune releases the bits of his spirit (in the form of flies) that infect and control others. It was how he controlled Oliver in Echo House and of course all the characters in De-Void.

We saw the same type of thing when they cut into William Barrow in Galvanize - I'm not sure how connected the two things are, they not stated it explicitly, but it's similar.