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In God of War Ragnarok's Valhalla DLC, you'll have to take on several types of bosses straight out of Ragnarok's story mode, as well as an all new boss fight at the top of Valhalla. However, there is a way to fight a familiar secret boss if you know where to look.
Unlocking the Forum Arena
To fight this boss, you'll need to unlock The Forum Arena in the Greek Labyrinth portion of Upper Valhalla. This can only be done after completing the main "story" and beating The Work: Part 3 - Benevolence.
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You'll need to unlock two other arenas in the labyrinth, which you can either do during The Work: Part 2 and The Work: Part 3, or wait until you complete the story and unlock that all at once.
The Aegean Sea Boat Arena can be unlocked as early as The Work: Part 2, by completing a Rift over near the East Wing (heading right from the Ascending Sands) and entering the door with the Skull Icon.
The Desert of Lost Souls Arena can be unlocked as early as The Work: Part 3, by completing 2-3 Rifts over near the West Wing (heading left from the Ascending Sands) and climbing up to a raised platform that has another door with a Skull Icon.
Once both arenas are unlocked, you can unlock the third and final arena at The Forum on the level above the Ascending Sands by defeating at least 7 of Valhalla's Chosen, which can be done through normal Rifts or through the other two arenas.
Once you're given the notification that The Forum has unlocked, climb up to the second floor overlooking the Ascending Sands, and look for a ledge leading to a large open arena with statues on all sides - the Forum Arena.
How to Fight the Secret Boss
Upon interacting with the Red Rift in the forum, you'll find yourself up against one of the 9 different Berserkers found at Berserker Gravestones during the Main Story (usually you'll fight one of the lower tier ones at first). If you need help fighting them, you can see our guides against each Berserker below:
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The trick to unlocking the true secret boss includes revisiting the Forum multiple times. In order for this to work, you'll need to spend at least two attempts at The Cycle defeating two random Berserker's back to back.
On your third visit in a row to The Forum, interacting with the Red Rift will instead summon the Berserker King himself - King Hrolf Kraki!
He's a lot tougher and more durable than the others, and can summon any of the other Berserker's weapons and attacks at will, making him an extremely unpredictable opponent. If you need help, be sure to read up on our Guide to Defeating the Berserker King.
Defeat Hrolf, and you'll get two special rewards: the Hilt of Skofnung Relic (the only one you can't get from Relic chests elsewhere in Valhalla), and the Flawless of Berserker Armor cosmetic to wear as you please!
