Dream Boss

A Dream Boss is the ghost version of a 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 similarly 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, except for 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 point of entry. 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

 * Dream bosses do not need to be defeated to unlock the Pantheon of the Knight as defeating the base counterpart will count towards the lock. However, the dream boss will still not be available in the  Hall of Gods.