Gameplan

At the mulligan, you make the go-plan on Bloodbloom. Do you have it? Do you want to keep it? Do you want to use it on Bane of Doom or Demonheart? If you have both it and the Bane of Doom, that's probably a combo you want to keep. Otherwise, it all comes down to your mood and how bold you're feeling, but the safest bet might be to throw anything that costs more than 4 mana back.

Your primary objective in the early game is to survive. Outside of Bloodbloom shenanigans, Warlock does not offer tools at the early game for furthering the win condition, so optimally you'll stall and keep the board clear until you can play Voidcaller or Skull of the Man'ari. If you didn't play the Bloodbloom on turns 1-3, its primary use especially against slower decks turns to Ectomancy.

[Hearthstone Card (Mistress of Pain) Not Found] is an early target for Bloodbloom into Demonheart - I used to run Void Analyst instead, but the +1/+1 buff turns out to be rather insignificant on already big minions. Mistress of Pain is also an MVP against aggro.