That guy is... awful, actually.
Woljif guesses this shouldn't exactly be a surprise, what with the whole "powerful demon" thing. You don't get to be a powerful demon without selling out some friends, and once you've done that a couple of times, just raping a mortal woman so's she can bear a tiefling child that will grow up to be a "destined vessel" for you to keep backstabbing and raping your way through life, eh, what's the big deal?
No, the weird thing is that he seems to've thought Woljif would actually go for that shit. What, was he born yesterday? "You'll have the power", "we'll be equal partners", "vengeance on everyone who hurt you", give him a break. Woljif knows a conman's pitch when he hears one. He's not even tempted, honest.