Hearthstone's new expansion hands you all four Old Gods and then tells you to pick one. Reign of the Black Empire went live on October 20 with 135 new collectible cards, and its centerpiece is a deckbuilding rule: C'Thun, N'Zoth, Yogg-Saron and Y'Shaarj are all in the set, but only one of them can go in any deck.

Each Old God comes with four unique abilities that Blizzard says can swing a match. Whichever one you pick, the rest of the deck gets built around it.

Assemble lets you build your own minions

The new keyword is Assemble. It lets players combine minions from a curated pool into custom creations. Blizzard's pitch is that it rewards tailoring your forces to your strategy and discovering devastating combinations.

The other faction in the set is the Titan-forged, the constructs the Titans built to fight the Black Empire. They're the counterweight to the Old Gods and bring their own tools for players who would rather fight the tentacles than feed them.

Journey moves the story into the Journal

Patch 37.0 also adds Journey, a new campaign layer that lives in the Hearthstone Journal. It pulls story, Journey Quests, rewards, events and seasonal content into one track that unfolds across the whole expansion, with voiced vignettes and lore entries. Achievements are now called Feats, with the same challenges and rewards under the new name.

A fresh Rewards Track ships alongside the expansion. Tavern Pass owners who reach level 100 claim a Diamond Rajh card.

Shop purchases now earn Tavern Tender

The change with the most long-term weight might be Tavern Rewards. Starting October 20, eligible purchases in the Hearthstone Battle.net Shop earn a currency called Tavern Tender at no extra cost. Players redeem it in a Tavern Rewards Vault on Battle.net for a rotating mix of packs, signature cards, card backs and hero skins.

In plain terms, it's a loyalty program for people who already spend money on the game. Blizzard says more details and the full vault lineup are coming soon. Tavern Rewards is available in every Hearthstone region except mainland China. Separately, a free weekly reward drops in the Battle.net Shop every Tuesday at 10:00 a.m. PDT, which is 1:00 a.m. Wednesday in the Philippines.

Arena already has the new cards

Arena players got a head start. Patch 37.0 went live on October 13, ending all ongoing Arena runs and starting a new season that folded Reign of the Black Empire cards into the pool a week before launch. The 12-win reward in Underground is now the Il'gynoth hero skin for Demon Hunter.

Reign of the Black Empire is live now. Blizzard's full 37.0 patch notes cover the rest of the update.