Hearthpwn

So having actually used the card now, I think it's pretty good. The invoke cards are both really strong for zoo style decks, the hero power is great, the biggest problem is honestly the battlecry. The variance on it is nuts. Sometimes you get nothing but imps, other times you get a reasonable board for how much time you have to invest in upgrading it, and even then without Voidlord and Doomguard, there's no really amazing high roll or anything.

The odds on it will get significantly better next year after the rotation (most of the garbage demons are in Witchwood and especially Boomsday).

 The Warlock Invoke cards are outrageously bad though, on the verge of being unplayable to not straight up lose you the game on Turn 5.

Fiendish Rights is pretty good in the deck you're building, the rest are okay, they're all minion based which is good.  They're also all fairly cheap. 

Galakrond Warlock is weird because I think it's kind of a midrange zoo deck, and in that context, Galakrond's hero power is pretty good. I wish the demon pool was a little more consistent, considering all the random demon effects (the difference between getting a jumbo imp and a flame imp is so wild).

I think one thing that's cool about Invoke, is because there's a cap to Galakrond, you really can be a bit more choosy about which invoke cards you want to play.