Neo Quest Druid v1.0

Mulligan choices will be updated as I get to play more of the deck. These are just general ideas of what you should mulligan for.

Worthy Expedition is almost always the best play on turn 2. It adds to your quest completion early on while also replacing itself with a card that has synergy with Ossarian Tear. Crystal Merchant is kept for the same purpose, on turn 3 it has a solid chance of surviving for more than 1 turn as well as adding towards your quest completion. Keeper Stalladris can be played as a 2/3 into aggro decks where his effect isn't very relevant or when kept against Midrange and Control decks it can provide insane value when combined with any of your Choose One cards later on.

Against early game decks you want to keep early drops to contest the board and removal to make sure you survive long enough to bury your opponent with your completed quest. It is important to note that against aggro your main goal is to survive because it's very hard to lose to the late game with this deck. When playing against aggro you shouldn't force yourself to play off curve to try and complete the quest. Don't use your AoE or removal too late and lose! 

Against Control decks you just want to complete your quest as fast as possible. Because of this you should keep cards like Worthy Expedition and Crystal Merchant so you can still play proactively while trying to complete your quest as fast as possible. Crystal Merchant is especially good since a 4 health minion is very hard to remove in the early game so it's really easy to draw many cards off of it. You should also keep any big payoff cards since you won't get punished to keeping high costed cards and you want to try and pressure your opponent as soon as you complete the quest.