Grimm

In his regular appearance, Grimm is a slender dark being covered by a multicolored cloak, with a gray exterior and a red interior. His face is pale with red eyes, and underneath his cloak, his body is scaled and red. As the Nightmare King, Grimm's body turns entirely red, with his cloak having a maroon color. His face remains pale and his limbs remain black. In his staggered form, Grimm resembles the Grimmchild's third form, only his eyes are glowing red and the rest of his body is black.

Grimm, throughout all of his interactions with the Knight, remains polite and respectful, bowing in shows of respect to them on several occasions. He is dedicated to the part he plays in the Ritual, and has a flair for theatrics, keeping with his persona of the leader of a traveling troupe. He views battle as a form of dancing and in combat shall unleash moves that cause his always nearby audience to cheer.

His respect extends to the Godseeker, for when summoned to do battle with the Knight before her, he shall again bow towards her. Dreamnailing him shows Grimm is in fact delighted to be in Godhome, viewing it as a pleasure to take part in the Godseeker's quest to find the strongest creature in Hallownest.

Troupe Master Grimm is both a quest NPC and boss introduced by the Grimm Troupe in Hollow Knight. He is the main character behind his quest. Nightmare King Grimm is his Dream form. Grimm is the master of the Grimm Troupe, a mysterious travelling circus. In truth, Grimm and his Troupe travel from the Nightmare Realm to wherever the Nightmare Lantern has been lit by acolytes.[2] They gather Nightmare Flames from ruined lands to fuel the sinister being enslaving the Troupe, the Nightmare's Heart.

Their ritual to feed the Nightmare's Heart consists of feeding first a Grimmchild with Nightmare Flames. They then slay the Nightmare King for it to be reborn anew through the Grimmchild. Grimm and his Troupe set up tents in Dirtmouth as soon as the Knight has lit the Nightmare Lantern. Inside the main building, Grimm appears to them in a show of red light and smoke. The Troupe Master is aware that the Knight called them with the Lantern and offers them the choice to participate in their Ritual.[5] He then gives them the Grimmchild and entrusts them to collect the Nightmare Flames gathered by his Grimmkins throughout Hallownest.

With each set of three Flames gathered, Grimm has the Grimmchild consume them to grow. After the second set, the Troupe Master tests the Knight's strength in a fiery, theatrical battle, in preparation for their confrontation with the Nightmare King. He also rewards them with a Charm Notch.

After collecting the third set of Flames, Grimm can be found sleeping in his quarters. As such, he is ready for the Knight to use the Dream Nail on him and enter the Nightmare Realm. If they successfully slay the Nightmare King, the Ritual is completed, and the Troupe leaves Hallownest before the Knight wakes up. The Troupe also disappears if the Knight helps Brumm banish them instead of facing the King