Stronghold – “The Barbarian Seven” [Campaign 6, Mission 3]

Can you tell me where the 7th fort with the veteran snow walker is hidden?
I've explored the entire map, but I can't find it anywhere.
Where should I look for it approximately?

Added 9 minutes later

The snow walker lives in a dungeon; the entrance is different from the entrance to the Necropolis island.

There's nothing in the second dungeon, only a forge guarded by elementals.
Or did I miss some other dungeon?