Nightmare Outfits Quest

Complete Mission 1 to 4 in Dreamer's Challenge Quest and then use a Document of the Follower.

Complete Mission 5 in Dreamer's Challenge Quest (hand over 500 Demonic Essences) and then use a Document of the Officer.

Complete Mission 6 in Dreamer's Challenge Quest (hand over 1000 more Demonic Essences) and then use a Document of the Leader.

How do I obtain these documents?

You can receive them from someone who has handed over 3000 essences (mission 7 of Dreamer's Challenge Quest. Alternatively you could hand over 3000 (total) essences to receive them yourself.

How do I travel back to the NPC after completing mission 4?

You'll need an Orichalcum Pearl. Search for the Knightwatch Tower and enter one of the portals in it.