You get the Hunter Dreambane chest piece by completing the Shadowkeep Essence of Fear quest, then turning it in at the Lectern of Enchantment on the Moon. The Essence of Fear is the Dreambane chest armor path, and it typically requires killing Hive enemies on the Moon before you can claim the reward.

How to unlock it

  1. Pick up the Essence of Fear from the Shadowkeep progression or the Lectern on the Moon.
  1. Complete the quest objectives, which involve defeating Hive on the Moon.
  1. Return to the Lectern of Enchantment to cleanse the essence and receive the Dreambane chest piece.

If you already got one

If you dismantled the chest piece, you can usually get it again through the relevant Dreambane essence path or by re-acquiring it from the Moon progression systems tied to Shadowkeep.

Extra note

Some players confuse the campaign steps with the armor reward steps: the Shadowkeep story gives Dreambane pieces as you progress, and the chest is specifically tied to the Essence of Fear reward path.

TL;DR: Finish Essence of Fear on the Moon and turn it in at the Lectern of Enchantment to get the Hunter Dreambane chest piece.