Trying to figure out how to open the gate to Northri Stronghold in God of War? This is a hidden area you might stumble across once you reach the Lake of Nine. You don't go there as part of the main story, so, like Veithurgard, if you're not on the hunt for treasure maps or other collectables, it's easy to miss.
If you do happen to stumble into the area by chance, you'll find your way barred by a locked gate and a mechanism used to open it. There are no clues about what you have to do to access the area, so I'll save you some frustration and help you out. There are some mild spoilers ahead, so click away now if you'd rather not take the chance. Here's how to open the Northri Stronghold gate in God of War.
God of War Fafnir's Hoard: How to get the Northri entry stone
You need to complete Fafnir's Hoard, one of Sindri's Favors—or side quests if you prefer—to get the entry stone required for the mechanism on the gate of Northri Stronghold. This favor becomes available when you return to Midgard after completing The Light of Alfheim story quest. Speak to Sindri at any of his shops to pick up the Fafnir's Hoard favor.
The quest marker takes you over to the west of the Lake of Nine. You can get there by boat by sailing under the ribs sticking out of the water there. Travel up Fafnir's Ravine until