To Unlock Niflheim Realm in God of War you must find 4 Niflheim Language Cipher Locations. They are in the purple cipher chests that have a “face” lock. Niflheim is an optional realm that consists of a randomized labyrinth. The best armor in the game can be found there, as well as the last upgrade for the axe. It plays an important role in the endgame to get the best gear possible.
Below are the locations of the 4 easiest Niflheim Ciphers. None of them are missable and they can be collected in any order (still after the story in free-roam):
#1 – The Mountain – 0:05
This one is located at the Mountain Summit, the very top of the mountain (by the “Summit” Fast Travel Gate). It’s in a hidden side area. When you come from the Summit Portal (from the tree where you first met Mimir), go across the mountain pass back towards the mountain. On the left side of the path there’s a little part where you can press to climb down. Don’t blink or you’ll miss it. The second screenshot shows the spot where to climb down (it’s in the outside area, not inside the mountain). After climbing down the chest is in front of you.
#2 – Lookout Tower – 1:04
Lookout Tower is a Region on the right side of the Lake of Nine (east). It’s a tiny area, the purple chest is on the right side of the beach where you can dock your boat. It’s behind some spikes. To make the spikes go away, hit the signpost on the left side of the island.
#3 – Ruins of the Ancient – 1:36
The Ruins of the Ancient Region is in the top left corner of the Sea of Nine. There’s only one Stone Ancient enemy walking on there and a purple chest, very easy to spot. It’s one of those islands you’d never go to if you didn’t go looking for it, as there’s no real reason to ever go there during the story.
#4 – Coucil of Valkyries – 2:02
The Council of Valkyries Region is in the north of the Lake of Nine. When facing the two big statues overlooking the Mason’s channel (screenshot 2), there’s a little beach on the right side. Dock the boat there, walk up the beach, and you’ll notice 2 red explosive crystals. Have Atreus shoot electric arrows at them (screenshot 3) to blow up the rubble on the path. Then you can reach the purple cipher chest around the corner (screenshot 4).
There are more than 4 but these are the easiest to get. After getting all 4 ciphers, go to the Realm Travel Room and select Niflheim as your destination. Finding all language ciphers is also required for trophy “Trilingual”.