Since it says play (and not just summon), I would assume it will trigger battlecries with random targets. In that case, this is scary looking card with very high potential, useful in almost any scenario. Probably one of the most powerfull dragon legendaries.

It’s still just one turn thing, where your opponent decides when to float that 1 mana.

Way to situational and only increases cost of hero power for next turn. Would be better if it increased the cost for several turns or at least until it is removed.
In control you would rather play removal, midrange decks care more about bigger treats and more aggresive/zoo/tempo decks would prefer Hystory Buff with same stats, but more tempo oriented effect.

This reminds me of Surrender to Madnes for priest, except it costs 3 less and essentially only punishes you for 1 mana. This is obviously much better, especially in some kind of tempo or zoo decks. Heck, even some kind of dragon druid would be happy to use it.

After giving it a tought, I really don’t see why players see this card as bad. It is obviously very good and versatile midrange/tempo card when copying anything with at least 2/2 stats. The only question is what kind of deck will want to use this. My guess would be some kind of midrange deathrattle based deck, perheaps with a dragon package since dragons have always been more tempo oriented.
I had quite some success with tempo deathrattle deck in pre-wild event meta, when the deck was very underrated in my opinion.

Imagine playing Thekal on 3, just so your opponent coins this out on 4 😀
On more serious note, interesting tech card which will probably mostly hurt warrior and partially druid.

Solid explorer, not to mention it is really cute. Probably a worthy inclusion in any midrange or control paladin deck.

They have wretched reclaimer.

Unfortunately I agree with you. There are some options with wretched reclaimer, but those are quite inconsistent and rather slow.
Nevertheless, I will try to make it work somehow for the art alone.

Damn, pardon me.. I read to fast and thought it was a battlecry.. Being a deathrattle makes it much slower.

That’s one hell of a sick card art.
Not much to say about it: bigger and better duskbreaker, arguably even better than netherwing for warlock.

Flavorwise, it is kinda weird to see hunter getting a hammer as a weapon. Those were usually reserved for paladin and shaman. The name is also suggesting that it should be wielded by shamans since they were always related to storms and lightning.
Powerwise, it is strong for any dragon based decks, even highlander.

Typo: not necessarily all.

It will be as usual. Last marked card reveal is actually reveal stream on official hs channel, where they reveal few of the cards by playing with them. After the stream, they reveal all the remaining cards via social media and whatnot. Majority of those dumped cards are pack fillers, but necessary all.

There is no reason not to run this card with even a handful of dragons. Heck, it even has vanilla stats (arguably 4/5 is better) so it doesn’t cost you tempo. It seems to me that card is on the same power level as Prince Keleseth, where you will often mulligan for it when playing a midrange or even control dragon deck.
It will probably single handedly carry all sorts of dragon decks. We might have to re-evaluate revealed dragons in regards to this one.

That is exactly what I said in my first comment, that slower warlock needs a more reliable win condition.

It is also true that if you survive against aggro against turn 8, you have probably already won.
However, midrange decks are a thing and against those in particular, this can be a strong card since they usually don’t run that much hard removal.

As for control, they will always have problems against midrange decks that can generate way too many treats for all the removal. That’s why highlander hunter, highlander mage and highlander paladin are favourites against control warrior. Hence, if some kind of midrange dragon handlock emerges, it might be quite good against control decks.
Telling what the meta will look like and what decks will be great is of course too soon and only time will tell.

Being a c++ developer I would have written
bool has_taunt = opponent_has_lethal ? false : true;

Well, if midrange or even aggro player decides to ignore it and go face, you just say thank you for free 6/6s and win on backswing. The only problem is that it costs 8, which might be too late sometimes.
As for control matchups, Expired Merchant exists, which can result in multiple boards.

If translation is correct, this is “must remove” target that can be protected by taunts. Unlike other similar cards that are triggering self-damage effects on your turn only, this one triggers on your opponents turn as well, punishing any player who dares to attack face.
Flavourful and strong, but slower warlock still needs more reliable win condition.

By taking their Kingsbane, you take the win condition. You don’t need to buff it or even use it. So it will work for all classes.