How to Unlock Hidden Archetypes
[N’Erud] – Found outside the map (4 stalagmites mark its location on the edge of the fog).
[Yaesha] – Purchased (15 essences) at the Bloodmoon altar.
[Losom] – Walk near large drain openings until you get pulled in by the Manticora (fake death screen leads to a boss fight).
[Root Earth] – Use the Dreamcatcher melees weapon on the walkers’ dream.
[The Labyrinth] – Presumably hidden behind the labyrinth red corrupted door requiring a key that will only reveal iteself by being corrupted in the labyrinth.
Just beat the game.