The next major expansion for Blizzard's popular card game Hearthstone has been announced. Coming mid-April is The Witchwood, which will add a total of 135 spooky new cards to Hearthstone's ever-increasing collection. Players can pre-order The Witchwood starting today, with Blizzard's standard 50-pack prepurchase bundle offering 20 additional free packs and an exclusive card back.

As with most major Hearthstone expansions, The Witchwood will add two new core mechanics to the card game: Echo and Rush. For Echo, players will be able to play multiple of the same card if they have the Echo keyword, and the mana too. Rush will be familiar to players, as it functions much like Charge, however Rush cards can only attack minions on the turn that they're played.

Some players may be initially disappointed by the straightforwardness of the two new keywords, but it's this relative simplicity that will allow the Hearthstone team to get creative with how these new abilities are applied. Any stronger and the keywords would be too strong, much like how Charge can be. Echo and Rush will allow for much more malleable decks and counterplay.

Even more exciting than new keywords is the introduction of the all-new single-player Monster Hunt game mode.  And best of all, Monster Hunt will be free for all players come The Witchwood's launch. Monster Hunt gives players one of four unique heroes, each with special hero powers. Players will then take on a series of up to eight increasingly challenging battles, wrapping up with a boss fight.

The twist for Monster Hunt, beyond the fun new heroes, is the gear mechanic. After defeating an encounter, players can improve a piece of loot within their deck. Then, further along in the hunt, players can add special cards to the deck that empowers the player's hero power. Monster Hunt should provide a challenging alternative to the competitive grind, come The Witchwood's launch.

As for the cards within Hearthstone's The Witchwood expansion, players will have to wait. A half-dozen cards are available to peruse on the official website, but the vast majority are left to reveal. Blizzard will reveal them slowly between now and launch, likely with the help of dozens of Hearthstone community members and content creators. Stay tuned for more information in the weeks to come.

Hearthstone is available now on PC and mobile devices. The Witchwood expansion launches mid-April.