My theory is that the nephilim were corrupted by Lucifer and became Princes of Hell. I’m pretty much basing this off the fact that Azazel and Jack have the same color irises.
In terms of what’s going to happen to Jack, I personally think he’s not going to be 100% bad and it might be up to Sam to relate to him and help him defy the destiny that Lucifer seems to think he should fulfill. ‘Cause, you know, Sam had that whole boyking and vessel for Lucifer thing and if Lucifer is the new King of Hell, that technically means Jack’s next in line and a potential vessel for Lucifer (if a nephil can be possessed).
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