'Hearthstone' expansion mines 'Warcraft' heritage

The latest addition to free digital card game "Hearthstone" makes the most of its connections to giant MMO "World of Warcraft."

First launched in January 2014 after a five-month closed beta, the one-on-one "Hearthstone: Heroes of Warcraft" is adept at balancing the accessibility of a pick-up-and-play card game alongside devoted service to longterm "Warcraft" fans.

The name of its July 23 expansion, "Curse of Naxxramas," references an area introduced to "World of Warcraft" in 2006, while the floating necropolis's boss, an undead mage called Kel'Thuzad, can be traced back to 2002.

Though free from the off, "Hearthstone" players can purchase additional decks of cards as well as entry to a competitive Arena mode.

And the accessible nature of "Hearthstone" means that new players end up learning about the characters behind "World of Warcraft" almost by accident.

In this case, five batches of new cards form the "Curse of Naxxramas" expansion, each corresponding to a thematically distinct geographical quarters.

The Arachnid Quarter is first up, available from July 23, and offered for free to anyone who starts playing through it within the month; the four other quarters are to be deployed a week apart, available for a fee of 700 gold -- accrued via completing in-game tasks or amassing Arena wins -- or, in more traditional monetary terms, for $6.99 (€5.99) each or $19.99 (€17.99) for four.

With game studio Blizzard Entertainment unveiling the Arachnid Quarter on Facebook just prior to launch, Kel'Thuzad is joined by a number of veteran "World of Warcraft" characters, including the plague-ridden Baron Rivendare and a clutch of venomous spiders.