2x Mortal Coil
2x Elven Archer
2x Shadow Bolt
2x Drain Life
How does it work, then?
Two words: Card advantage. You can achieve this by using your hero power, or those Novice Engineers, just be aware that some of these cards have a random discard condition so make sure anything super-valuable is out of your hand otherwise you risk losing it. Oh, and don't forget the hero power card draw has a 2 damage penalty so try to balance card draw with having enough life to survive.
Hellfire offers fantastic board clearance but as it deals 3 damage to ALL characters, not just your enemies, you'd ideally throw it down when your side of the board is looking pretty empty. If you do need to use it at other times remember to use the attack power of any minion who's about to meet their maker BEFORE you Hellfire them, and to play new minions afterwards to keep them from a scorching.
Poyo says :
Newcomers might be wary of the Warlock hero power which deals damage to said hero in exchange for card draw. We asked Poyo to explain why it's actually a very good thing: “Let's compare Rogue and Warlock. How different is it if your opponent plays a 2/1 minion and you use your hero power to create a 1/1 dagger and attack that minion of his? How different is that to using the Warlock hero power? Your opponent lost a card so you created the same amount of card advantage.
It does force a particular playstyle. Warlocks are either going to be really aggressive or control. You're playing Twilight Drakes, Molten Giants which are affected by your health, Mountain Giants which are affected by how many cards you have in your hand, and so on. In general you play 25 minions and 5 spells and those 5 spells are damage to your opponent's face or maybe taking out a fat minion that comes on the board.
“The general principle is the same. You unload your hand on the board and you go for the face. When your opponent makes a move and puts a minion on the board you simply try to make an efficient trade that would give card advantage. When you have nothing else to do, you draw cards with your hero power and put down more and more and more.”
Dust's no object, you say?
Take a peek at the Legendary Warlock Control Deck