Eww. Same cost as demonfire, without the flexibility to use it as a damaging spell, with a MAJOR drawback if played early - all for +1/+1? Horrible :( I'm not as down on some of the cards as seemingly everyone else but this is atrocious.
Would you give your opponent a permanent mana crystal for +1/+1 on a demon? Because that's essentially what you're doing here, while sacrificing the damage flexibility of demonfire.
They could have at least made the drawback something like 3 damage to your hero. At least then it'd see some play in aggressive decks that don't particularly care about their health (and even then, the loss of ability to use it as a damaging spell might make it not worth it over demonfire). But giving opponents a way to get their taunts/removals out faster kills it early game and it's pretty mediocre if you're sitting on it until 9 mana.
This seems to compare unfavorably to Rampage, which is already a card that never sees use despite Warriors haven't much better synergy and opportunity to use it than Warlocks have to use this card.
I hate to say it because I'm the first to tell people to calm down with their assumptions that a new card is going to be bad just because they haven't figured out how to use it yet, but... this card looks pretty bad. XP
P4wnyhof played a fun deck today that went ~31-13 at legend with power overwhelming arcane golem and faceless manipulator for potential 10 mana 24 dmg burst. This could be a thing in a deck like this, aggressive-midgame or even late game kills.
Actually a really fascinating zoolock/demonzoo card. Just like Arcane Golem the trick is to have your opponent dead and be on to your next game before that mana crystal even matters. I don't agree with people who think it's so terribly horrible, but I do think it'll be difficult to play this because it'll just get your opponent to Belcher or even Taz'dingo that much faster. Very interesting, though, and I'm always up for new cards that have strong deterrents to justify their power.