Michael became petrified beyond description.
On a supernatural scale, there is very little more horrifying than feeling your power be ripped away from you.
No matter how hard you try to fight it, you are unable to hang onto that which is practically your birthright.
If Michael's reaction was poor, Lucifer's measured response was abysmal.
"Boy… I am your father. Release me now."
The child didn't even blink, he just tilted his head in an uncanny manner.
He remained unresponsive, but Michael had the strangest feeling that the child was fully capable of if.
Rather, he was just choosing not to.
That was by far the more unnerving of the possibilities. And Michael's fear of the child only grew from there.
"Why is he doing this?! Stop him!"
Lucifer was trying not to show it, but he was just as powerless as his brother here. And even more fearful.