BlizzCon, Blizzard Entertainment’s yearly convention event, is only a week away, and it seems that the American developer intends to make a pretty big Hearthstone-related announcement.

BlizzCon is already a pretty big thing for all of Blizzard’s fans, consisting of a ton of activities and being a wonderful source of spoilers for the future of the developer’s video games, and as an added bonus, this year’s edition will conclude with a concert from none other than rock superstars Metallica.

Big announcements regarding the developer’s existing and future projects are a norm, and it appears that we just got confirmation that among them, there will also be some good news for fans of the company’s collectible card game, Hearthstone.

A bunch of teasers

Blizzard has been sending out various postcards depicting blueprints for various Hearthstone cards, together with the cryptic message “Making plans for BlizzCon – I hope you like my invention!”

Many websites received such notes in the mail, and you can browse the gallery below to see them. From Harvest Golems to Demolishers, Repair Bots and Alarm-o-Bots, all the cards seem to share a similar theme.

All of the cards featured in the teases are mechanical in nature, artificial life forms of Goblin design. In addition to this, Blizzard also revealed the card back for November, featuring obvious Goblin engineering elements.

Back in September, Hearthstone Production Director Jason Chayes revealed that Blizzard is working on a new expansion for the collectible card game, an add-on that would be introducing 100 new cards into the mix.

A subject ripe for speculation

BlizzCon seems like just the place to announce Hearthstone’s first card expansion. The Curse of Naxxramas, the game’s first single-player adventure, introduced over 30 new cards into the already extensive pool that gamers can make use of while building their decks, but the addition of over 100 new creatures and spells will thoroughly shake the metagame.

The mechanical-themed teases could be a sign that that upcoming add-on has a Goblin (or Gnome) theme, focused on daring contraptions and more oriented toward technology and tricks than arcane powers.

Then again, the artificial life forms featured in the postcards could also mean that Blizzard is getting ready to release Hearthstone for Android devices, as the company promised to have the game out on the platform by the end of the year.

In any case, as BlizzCon is kicking off on November 7, we won’t have to wait too long for the official announcement tied to the mysterious packages.