I'm really liking this theme of "health changing", and this looks like a very flexible and fun way to lower the cost of a high-stat card.

Looks more like  a priest card than a warlock one.

0 mana 8/8. If there was a way to duplicate this into the hand, then you've just got yourselves a bunch of free giants.

Just a very strong card thats flexible enough to fit into any warlock deck, and some select priest decks.

and have returned.

At least 3+5 damage to own face, instant Turn 3 double Flesh Giants.

A very interesting card for sure, but it seems like it will more easily find a home in Warlock than Priest.  With how easy it is to damage your hero in Warlock, I could see a possible tempo or midrange self-damage warlock come to fruition with this plus the other P/W card revealed today.  The issue in Priest is that there are some matchups where you will not be able to consistently heal your face.  Additionally, Warlock self-damage cards have above-average stats for the cost to compensate for hurting your face, making it easier to play them on curve while Priest healing effects are more conditional in getting value (your hero has to be damaged) and their healing takes up power budget instead of allotting more.  All that said, Priest's quest saw amounts of success despite running into similar issues, so this might find a home there as well.

Pretty much 0 mana giant on quest lock, free tempo in mid/early game its even better than mountain giant in most cases 5 stars

Yes, but also Disciplinarian Gandling looks more like a warlock card than a priest card. Maybe all of theset will always weight more on 1 class than the other.

Not sure what deck needs a plain 0 mana 8/8 right now, but this is easy enough to discount in pain zoolock that it could be very good at 4 or 5 mana as a curve topper.

The discount is easy to obtain specially for an Handlock. Can fit well in other lock deck meanwhile for Priest is difficult to abuse since healing can't be done with 30 hp. So...this is a lock card only probably

If you tap 3 turns in a row it's 5 mana 8/8, definetly not mountain giant but late game it is, control lock could use 0 mana 8/8s.. Shadow flame, defender of Argus, sunfury protector, like og hand lock.. Twilight drake is still a thing.. Well mountain giant isn't this replaces the card. 

Looks like a pretty nice giant for Warlock that’s easy to reduce the cost of. Bit more awkward for priest, but still not too hard

This certainly is interesting. I would be happy to open one or two of these to play around with, though I am not sure exactly what deck wants them right now. I guess a zoolock type deck with Darkglare and Flame Imp and stuff. Priest is kind of tricky since healing your face is a bit harder to do than damage it. I am pretty sure somewhere a deck is going to really want two copies of these, I am just not sure exactly what that deck looks like.

For anyone who doubt of its potency for Warlock, I'd like to remind you that a giant was once nerfed and hall of famed because it was doing a little too good into Warlock's lists - I could be wrong - who knows?

The last two class giants printed for Priest and Warlock saw minimal play during their initial release before being substituted for more efficient minions.

Grave Horror was a 12 mana minion that was discounted by (1) for each spell you cast on your turn and Jumbo Imp was discounted by (1) for each friendly demon that died while it was in your hand.

This Giant will most likely see home in a control deck, which Priest and Warlock can excel at, where damage mitigation is key. 

This means taking damage and restoring it.

Warlock has good tools that help them TAKE damage, their default hero power helps them deal 2 damage to themselves while they draw this card. There's also a long list of spells and minions and standard and wild that allows the warlock to hurt themselves to receive a positive benefit, Rain of Fire has been a popular mention already, but their class healing is very very weak, with NetherBreath and Aranasi BroodMother requiring deck construction to utilize them the best.

Priest has the opposite problem, they can restore 2 health with their hero power, but their library is more geared toward self help than self hurt. Priests are able to mitigate damage taken but they won't be able to be proactive on the damage end.

Cards such as this and the Brittlebone Destroyer I believe will help open doors to old archetypes and decklists of Warlock and Priest - self harm and Obelisk Priest. Warlock received some cards that didn't see much play with Neferset Destroyer and Diseased Vulture, two cards that reward self punishing plays. Priests Obelisk quest saw some fairly competitive play in Ulduum, and a deck list that requires you to mitigate what your opponent damages sounds like it'd be a shoe in.

I believe this would make this giant a contender for control decks, but not the popular handlock or resurrect priests we've seen since they're overtaken with the Galakrond package since DoD

Firstly - the theme is magnificent. This is as dark as I was hoping the Warlock/Priest combo would be. A fatty nose with legs. Why, I could see this bloke shopping at Walmart!

Secondly - does this trigger for 'each time your health changed during one of your turns', or 'each time your health changed during one of your turns?' That is to say/blather on, does its cost reduce by one for each turn during which your health changed, or for each time your health changed, turns notwithstanding? I'm guessing it's the first, because if it were the second, you wouldn't need to state 'during one of your turns' - the text would be 'each time your health changed this game'. 

Terti-idon'tcare-ally - even though that means that our new big honker ain't so strong as the other folks here think, since cards like Spreading Madness would only reduce its cost by one, it's still flabbergastingly good! (Get it? Flab? haha. wee.) Damage yourself on turns 1-4, and voila, you have a playable 4-mana 8-8 for turn 5, ready to be copied, taunted, and Shadow Word: Ruin'd.