Board Thread:Television/@comment-1713281-20151029033607/@comment-11220539-20161013174251

It all ties back to the Darkhold. With that in mind I've got two theories:

1. The spirit/demon/whatever in Robbie was summoned by Eli via the Book of Sins or

2. Eli IS possessing Robbie and the Eli that's in prison is some sort of magic duplicate, again created by the Darkhold.