"Well see we've come to a bit of an impasse then, because I cannot promise obedience if the proof doesn't prove what I need to know. But you can't offer proof unless I promise obedience.

What's a man to do about that then?"

Well.

"If you're The Devil in all their flame and glory, you'd know some things most oughtent aye? Shouldn't take a lot of energy to state a thing I'd know that no one else would be aware of now would it? Tell you what."

The pirate boldly went to try and snatch up the reservoir for a drink.

"You do somethin' only The Devil can do, tell me a thing about me that no one else would know. I'll be the happiest cabin boy you ever met, sound good?"