Dream Boss

A Dream Boss is a ghost Boss that is unlocked by defeating a specific living Boss and then striking their corpse with the Dream Nail. The Knight will be transported to the dream realm and must perform a short platforming sequence to reach the boss room, which will be set up in a similar fashion to the room in which the original Boss is fought.

Dream Bosses are significantly more challenging than their living counterparts, with much faster and more complex attack patterns, along with much greater health.

When defeated, a Dream Boss, with the exception of Nightmare King Grimm, will grant a certain amount of Essence, just like Warrior Dreams. There are six Dream Bosses in Hallownest.

Losing a Dream Boss battle
It's important to note that The Knight does not actually die during a Dream Boss battle. If the Knight dies, they will simply wake up next to the corpse. This means several things:
 * The Knight does not leave behind a Shade.
 * The Knight does not lose part of their SOUL Meter. (However, the SOUL meter still completely empties.)
 * The Knight does not lose any Geo.
 * The Fragile Charms sold by Leg Eater do not break, making Fragile Strength and Fragile Heart particularly good choices.
 * Steel Soul runs will not end.

Trivia
A dream boss' lock on the Pantheon of the Knight will unlock after defeating their normal version, with the dream version not being required. However, the dream boss will still not be available for fighting in the Hall of Gods.