The new Lost in the Park brings Feral Druid closer to being a viable deck than ever before. It's not top tier, but it's standing up quite well on the current ladder. These are the first days of the expansion though, it remains to be seen how it fares when the meta settles.

Game Plan

Against aggro you just have to keep clearing the board and if you can survive to quest completion you're likely to win.

Versus slower decks you can either try to deal lethal damage before they get to execute their game plan, or you can try to grind them out of healing and removal. In either case, you have to keep pressuring them, but if you're going for the grindier approach you should pick more value-oriented card from discover effects. If you're racing to lethal, you can use Savagery and Lesser Jasper Spellstone to clear the board while you attack face, but if you're going to grind it out, it's better to hold on to that efficient removal until the high-health minions hit the board.

Brann Bronzebeard can be used on turn 8 to gain double attack and armor from the quest reward. Generally you should have the quest complete by turn 6 or 7; depending on the match-up you may not want to wait for Brann.

Zola the Gorgon can be used to give you another copy of the quest reward. Since Guff the Tough counts as a beast, he can be resurrected by Witching Hour. Not only is an 8/8 taunt good value for 3 mana, this also gives you another chance to use Zola if you drew her after you already played Guff.

Mutanus the Devourer acts as either a combo disruptor or a late-game threat + value destroyer. The combo disruption is mostly useful against Mozaki and Ignite Mages, although my success rate has only been 1 out of 3 so far.

Mechanics and Micro-optimizations

Progress does not carry over across questline stages, so if you're for example at 4 out of 5 progress for the current stage and you plan to play Feral Rage and hero power this turn, you should use the hero power first to trigger the next stage and then play Feral Rage to get 4 out of 6 progress in the new stage (the other way around would put you at 2 out of 6 progress).

You don't always need to play the quest on turn 1. To not miss out on progress, you do want to play it before you first use your hero power, but you could play for example Tour Guide on turn 1 and then the quest on turn 2, such that your Guide can attack on turn 2. You could do the same thing with Nature Studies, but I wouldn't recommend that, since you'll know better what cards you want to discover once you're further into the game.

Tour Guide and Nature Studies are good cards to end your turn with, to set up a discount for the next turn that allows you to react to minions played by your opponent.

If you think your opponent might be playing hand disruption, make sure you can play the quest reward on the turn you get it.

Secure the Deck should count as a quest for Entrapped Sorceress. I haven't had that combination in play yet without also having the questline active, but sidequests did work with Questing Explorer in the past.

Mulligan

Keep the quest in all match-ups. Other good keeps for the early game are Tour Guide, Secure the Deck, Nature Studies, Entrapped Sorceress and Hench-Clan Thug.

If you're expecting aggro, hold on to Savagery and Lesser Jasper Spellstone.

If planning for a longer game, keeping The Curator can be worthwhile, to have something to play in the late game while making sure you'll draw into Alexstrasza the Life-Binder to finish off your opponent.

Replacements

Lost in the Park and Baku the Mooneater are essential.

The Curator could be replaced by Taelan Fordring or Ancient of Lore.

The other legendaries are optional and don't really need to be replaced by a card that fulfills the same role.

Other cards that I think could work well in the deck:

• Gnash or Claw
• Wild Growth
• Abomination and/or Baron Geddon
• Umbral Owl
• Questing Adventurer, probably only if you're running Secure the Deck though
• Kobold Stickyfinger or Harrison Jones, if you're seeing a lot of weapons
• Chief Inspector, if Ice Block is a problem
• N'Zoth, God of the Deep: we have big beasts, a mech, a dragon, a murloc and two quilboars — most games are decided before Alexstrasza the Life-Binder dies though

The new Rustrot Viper is efficient anti-weapon tech, but as a beast it has anti-synergy with Witching Hour. You could include it anyway, but I'd recommend trading it in unless there is a really important weapon to destroy.

Today I only saw Pirate Warriors (questline) use weapons but that's a favored match-up already, so in the current meta you probably don't need anti-weapon tech.

I would have liked to include Gonk, the Raptor in the list above, but sadly he's too expensive to be used effectively in this deck (I tried).