I am playing a Prince Keleseth zoolock deck in Hearthstone (see here or here for a decklist). I'm looking for guidance on mulligan strategy.
I've seen advice to hard-mulligan for Prince Keleseth. In other words, if you don't get Keleseth in your starting hand, the suggestion is to throw everything back. The rationale is that playing Prince Keleseth on curve makes such a large improvement to your win-rate that you should maximize your chances of drawing him (for instance, winrate if you get Prince Keleseth in your opening hand is about 73%; the next closest card is a 61% winrate if you get Corridor Creeper).
Is this strategy correct? Or are there circumstances where it makes more sense to avoid hard-mulliganing for Keleseth? Maybe there are matchups when you should also keep a good 1-drop (like Flame Imp or Kobold Librarian), if you have one, or maybe keep Corridor Creeper?
I do see from hsreplay.net that players do seem to be keeping certain cards (one-drops, Southsea Captain, Corridor Creeper) on the mulligan more than half of the time. This is more often than we'd see if players were hard-mulliganing for the Prince. In other words, the data suggests that a significant fraction of players must be following some other mulligan strategy. So which is the optimal strategy?
Best Answer
You don't hard mulligan for Keleseth. This is especially true for a top end heavy list that plays Doomguards, Cobalt Scalebanes, Bonemares and Gul'Dan.
Having a good curve in the current meta is far more important than playing Keleseth on turn two.
As a rule of thumb, when playing Zoolock you should always keep all 1-drops if not on the coin and a 1-drop and a 3-drop (for example Southsea Captain) if you are on the coin. Corridor Creeper is also a great keep if you have a 1-drop, especially if you are expecting early AoE (Duskbreakers) or a lot of trading (against other tempo-oriented decks like Paladin, Rogue or Hunter). Whoever drops the first Corridor Creeper in these match ups often wins the game.
In the upcoming World Championship there is one player (I think JasonZhou, not sure though) who is bringing Zoolock, it might be beneficial to check out his mulligans. Ant is another pro player who is known for being a great Zoo player.