Right now, there are 10 playable classes in Hearthstone, each with their own plethora of unique cards, mechanics, and playstyles. Each class has some of its own strengths/weaknesses, and within each class, countless different decks can be made to accentuate different strengths or to offset some of the weaknesses.
For this list, let's take a look at the Warlock Class. This class really plays very differently from a lot of the other ones out there, and in order to get the most out of it, you're likely going to be living on the edge. Let's go over some of the mechanics present in the Class, as well as some specific cards that can be very strong, in the right circumstance.
10 DEMONS
The Warlock Class is almost always going to be making heavy use of demons. Most of the demon minions in the game belong to the Warlock Class (and now the Demon Hunter Class).
Demons are generally some of the strongest minions in the game, though usually, they come with a bit of a catch-22.
9 INFLICTING PAIN
The thing you have to keep in mind with some of the demons is that they are going to deal damage to your own hero, either on summoning or when they attack another character.
The benefit is, these minions are generally stronger than others that cost the same amount of Mana. Just be sure you're going to get to make use of them before summoning, lest you give your opponent some basically free damage.
8 CHANCE
There's also a lot that comes down to chance with the Warlock Class. Tons of cards have effects that are dispersed randomly, that effect either being in your hand or on the board. Some games, this is going to really end up in your favor, with the fortunes smiling upon you as you rain down terror on your enemy.
In other games, that same fortune is going to laugh in your face, giving your opponent a truly easy victory.
7 DISCARD
Some of the strongest cards in the Warlock Class don't deal damage to your Hero. Instead, they force you to discard one (or more) cards. This isn't always permanent, but sometimes it is, and that cost can be severe.
This effect can be offset somewhat with a lot of smart deck-building and a little bit of luck, but it is never going to be a foolproof mechanic. Again, it comes down to chance.
6 GALAKROND
The Warlock is one of the classes that has access to Galakrond. This won't come as any surprise, but Galakrond can be a bit of a mixed bag with the Warlock because of, you guessed it, chance. Invoking Galakrond with this Class is straightforward. It summons two 1/1 demons to make use of in whatever way you see fit.
They can be killed with a certain card to restore 5 HP, they can be buffed, etc. Becoming Galakrond summons a certain amount of demons, depending on how many times he's been Invoked. These are random demons, so sometimes you're going to get the cream of the crop, and sometimes you're going to wish you hadn't even bothered.
5 ARANASI BROODMOTHER
One of the cards that has a heavy (and important) presence in a specific kind of Warlock deck is the Aranasi Broodmother. This is a 6-cost, 4/6 minion that, when drawn, restores 4 HP to your Hero.
While this might not seem like a huge deal, combined with the next card on this list, it can make an incredible difference.
4 PLOT TWIST
Plot Twist is a 2-cost spell that shuffles your hand into your deck and then causes you to draw that many cards again.
If you've got two Aranasi Broodmother's in your deck, the likelihood of you drawing one is pretty decent, giving you a lot of extra mileage out of that minion's Draw effect.
3 TWISTING NETHER
If you find your opponent has complete board control and you'd like to flip the table and start over, Twisting Nether is a good place to start.
This is an 8-cost spell that destroys each and every minion on the board, in essence resetting it so you can get back on your feet.
2 JUMBO IMP
At a quick glance, the Jumbo Imp doesn't look like it's going to be much help; a 10-cost minion that's an 8/8? That said, a deck full of demons is going to absolutely love this card; while the Jumbo Imp is in your hand, each time a friendly demon dies, it's going to reduce the cost by 1.
This is going to end up being an 8/8 minion that costs a heck of a lot less than 10 Mana. Who doesn't love that?
1 ZZERAKU THE WARPED
One of the crazier minions available, especially if you've got a Flame Imp or your Hero Power to follow it up immediately with, is Zzeraku the Warped. This is an 8-cost, 4/12 minion that, whenever your Hero takes damage, automatically summons a 6/6 Nether Drake.
This can quickly cause a board to get out of hand (in your favor) and your opponent is likely going to have to immediately deal with Zzeraku, or they're likely to regret it.