"The expanse of dream in past was split,
One realm now must stay apart,
The Nightmare's Heart is a higher being responsible for the Ritual of the Grimm Troupe. It is the deepest power within the Nightmare Realm, and also the one that controls the entirety of the Grimm Troupe.
- ↑ Nightmare King Grimm in Godhome: "Deepest power... the Heart..."
- ↑ 2.0 2.1 White Lady on the completed Grimmchild: "Success then for the scarlet heart, and irony, to use my spawn to grow its own. I know you creature, and the form time shall bring. You may be all and one, clan and master,"
- ↑ Troupe Master Grimm Dream Nail dialogue: "perfect tool to prolong the heart of Grimm."
- ↑ Grimmkin Master Hunter's Journal entry: "Burn the father, feed the child."