There are a total of 6 dream bosses in Hollow Knight that will reward the little knight with a total of 1,600 essence. All of the dream bosses are harder versions of the original bosses and fought in the dream realm. They are faster, have new attacks and some deal double damage.
The essence is used to upgrade the dream nail to the awoken dream nail. The awoken dream nail is used to access the White Palace, acquire part of the king’s soul charm and then eventually the good ending.
Requirements:
Dream Nail
How to find Dream Bosses:
- Failed Champion- 300 Essence
Located above the false knight fight in the Forgotten Crossroads:

From the original fight use wall jump to get above the platform:

There is a secret breakable wall that will lead you to the body of a Maggot.

Use dream nail to start the boss fight with the Failed Champion

- Lost Kin- 400 Essence
Located in the same location as broken vessel.


- Soul Tyrant- 300 Essence
Located in the City of Tears where we found the Soul Master

- White Defender- 300 Essence (Requires defeating all 3 Dreamers)
Located near the Dung Defender but hidden under a breakable floor

The floor is breakable just below the switch that opens the way to Isma’s Tear

- Grey Prince Zote- 300 Essence- (Requires rescuing Bretta, Rescuing Zote in Green Path as well as Deepest and the coliseum)
Go into Bretta’s House

There is an opening down into the basement

Bretta has a statue of Zote that can be dream nailed

- Nightmare King Grim (NKG)- No Essence (Requires a level 3 Grimmchild with three Flames)

Following the map, there is a large bug laying on the floor at the end of a hallway. Dream Nail the bug and head one room to the left

Here you will need to attack the fireplace to light the fire to start the Grimm Troupe Ritual
Now head back to Dirtmouth to find the Grimm Troupe has moved in. Enter the tent and talk to Grimm. After defeating Grimm you will be able to come back and fight Grimm again as the Nightmare King Grimm.

The fastest way to collect essence in Hollow Knight is to defeat the dream bosses. Even then, the little knight will need to collect more essence to get the awoken dream nail. The Easiest way to collect essence is to fight the dream warriors. There are 7 dream warrior graves for a total of 1,100 essence.