It’s finally happening: the world of Sanctuary is getting invaded by Azeroth’s biggest bad guy.

That’s right: The Lich King is invading mobile action RPG Diablo Immortal in a one-time limited event featuring still-living mass multiplayer online RPG World of Warcraft enemies and a ton of loot. This collaboration from Activision Blizzard, called Eternal War, is to celebrate the 20th anniversary of the long-running MMORPG. The limited-time event will bring your characters to a new boss stage called the Fallen Citadel, a multiplayer PvP arena called Cutthroat Basin, and a new legendary gem called the Mourneskull.

This being a mobile game, there’s going to be ton of login bonuses and some mobile F2P prerequisites to play the Fallen Citadel and fight the Lich King; you’ll need to earn special tokens -Frozen Boons- for the fight by completing your Diablo Immortal dailies and other activities tying in with the Eternal War event. The following can be unlocked for free:

• Mourneskull (Two-Star) Legendary Gem.
• 1 New World of Warcraft Weapon Skin.
• 10 Legendary Crests.
• Frostmourne Weapon Cosmetic
• Icecrown Pathway Portal

You can also earn the following weapon skins (per class) by partaking in the Eternal War:

• Shadowmourne: Necromancer
• Gorehowl: Barbarian
• Thori’dal, the Stars’ Fury: Demon Hunter
• Truthguard: Crusader
• Atiesh, Greatstaff of the Guardian: Wizard
• Thunderfury, Blessed Blade of the Windseeker: Tempest
• Remornia: Blood Knight
• Fist of the Heavens: Monk

The event will be happening from 13 November to 11 December, so jump right in if you’re still playing Diablo Immortal. Check out some gameplay below with the game’s exclusive Blood Knight and Tempest class.