https://www.gamespot.com/articles/hearthstones-halloween-event-comes-with-a-bunch-of/1100-6454158/

Blizzard announced today that Hearthstone is getting a new Halloween event. Called Hallow's End, it features a new mode, a special Brawl, a new Hero, and some free card packs. It takes place from October 24 to November 6.

During the event, players can check out a new dual-class Arena mode that allows you to mix-and-match cards from two different Heroes. At the beginning of each Arena run in the dual-class mode, you select a Hero, a Hero Power from a different class, and cards from both classes. You can also expect to see your Hero appear in a Hallow's End-themed costume.