The biggest massively multiplayer online game in the market is getting a ton of new content today.

World of Warcraft’s 7.1 patch is now live, which adds new missions, cooperative multiplayer action with a nostalgic dungeon, and balance changes for its classes. This is the biggest update to the massively multiplayer online role-playing game since its Legion expansion launched in late August. Patches like these are important for retaining players (and for a subscription-based game like WoW, making sure that money keeps flowing in), since the new content gives people a reason to stick around and keep paying.

The new dungeon,¬†A Return to Karazhan, is the centerpiece of the patch. The five-player experience is based on a classic World of Warcraft Raid, which was originally designed for 25 people to play¬†Karazhan is one of the most popular locations in the Warcraft universe, even becoming the basis for the latest addition to Blizzard’s digital card game, Hearthstone: Heroes of Warcraft.

Larger groups will get to play through the new Raid, Trails of Valor, which unlocks on November 8. It’s a shorter experience than the current Raid, Emerald Nightmare, having just three bosses. Still, it’ll give players a new end-game challenge until the launch of the next Raid tier with the Nighthold.

New quests will continue the stories of the Suramar region and one of Warcraft’s most popular characters, the demon hunter Illidan. Meanwhile, class changes look to make some of the weaker characters more formidable. You can check out the complete patch notes, including the specifics on class balances, here.