Opponent has a Daemon Prince, pays nothing (+/-0 points) and it turns into a Lord of Change. Meh, it was close enough for me
Like you say about Stern being bad, I'd genuinely prefer to pay the 40 points difference and take an ordinary Grand Master with the same equipment. That's equivalent to.... What, nearly one Grey Knight with a Psycannon? Not a big loss. And what I get in return does virtually the same thing, but is much better because I'd be allowed to give him Psy-bolts and some other useful things to boot.
See what I mean about ordinary IC's being just as good - if not better - than a lot of SC's? And given that in this case it's a GREY KNIGHT hero, that's pretty embarrassing....!