Grimm

Troupe Master Grimm is both a quest character 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.

Lore
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. They gather Nightmare Flames from ruined lands to fuel the sinister being enslaving the Troupe, the Nightmare Heart.

The Troupe Master has a charming and playful personality. As the Nightmare King, however, his self in the Nightmare realm, his thought are focused on his enslavement to the Heart. Their ritual to feed it consists of feeding first a Grimmchild with Nightmare Flames. They then slay the Nightmare King for it to be reborn anew through the Grimmchild.

Hollow Knight
Grimm and his Troupe set up tents in Dirtmouth as soon as the Knight has lit the Lantern. Inside the main building, he appears to them in a show of red light and smoke. The Troupe Master is aware that the Knight called them with he Lantern and offers them to participate in their ritual. He then gives them a 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 will 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 Troupe will have completed their ritual and leave Hallownest before the Knight wakes up. The Troupe will also disappear if the Knight helped Brumm banish them instead of facing the King.

Grimm can be summoned to Godhome by  the Godseeker's own ritual. There he will be conscious of his surroundings and delighted to participate, even though he is not native of Hallownest. He takes part in both the Pantheon of the Sage and the Pantheon of Hallownest. In the latter, the Nightmare King appears as one of the last three Gods at its peak. Even though away from the Nightmare realm, the Heart still watches over the Nightmare King's fight.

Behaviour and Tactics
Before the battle, Grimm will bow. If the Knight hits him while bowing, Grimm will screech at the Knight and will counterattack with the Flamespawner Attack.


 * Fire Bats: Grimm will open his cloak, sending three Fire Bats at the Knight. The Fire Bats start at the level of the Knight's head and poorly track the Knight's movement. Grimm remains stationary during this attack. Each Fire Bat's entrance is announced with a gout of flame coming from Grimm and reaching the top of the arena. If the Knight gets within arm's length of Grimm before he sends out all three Fire Bats, he will teleport to another part of the arena and send one last Fire Bat. This Fire Bat cannot be interrupted. This means that it's possible for Grimm to send out only one Fire Bat.


 * Dive Dash: Grimm will teleport in the air and wrap himself in his cloak until he resembles a drill and dive towards the Knight. Then he lands and follows up with a dash towards the Knight's direction using his arm wrapped in his cloak like a lance. Grimm tracks where the Knight was near the start of the dive and the dive can traverse the entire arena.


 * Dash Uppercut: Grimm will dash across the arena with a large swipe directly before launching into the air with an uppercut. At the apex of the uppercut, he disappears and rains five fireballs on the arena. The five fireballs rain down on the arena in set parabolas.


 * Cloak Spikes: Grimm will send his cloak into the ground, causing large twisted cloak spikes to jut up from the floor. The spikes reach to the top of the arena but there are large enough gaps between them to stay safe. The spikes are not dangerous until they are at their tallest. The spikes persist for about half a second.


 * Flamespawner: Grimm surrounds himself with his cloak and puffs out and spews tiny fireballs all over the arena. This attack occurs when Grimm's health reaches 75%, 50%, or 25%. This attack always occurs from the centre of the arena. The fireballs travel in five general directions. Fireballs tend to come at the Knight in sets of two, resulting in essentially a jumping puzzle. Grimm will stay in this form for nearly nine seconds. While he's in this mode, Grimm is immune to Nail damage but still takes damage from everything else. This will be the first attack he will perform if the Knight hits him during his bow.
 * Teleport: Grimm will teleport to a random place in the arena to perform an attack.
 * Skitter: If Grimm teleports on the ground too close to the Knight, he will Skitter away on all fours before resuming his attack. It is rare but possible that Grimm will begin a telegraph for one type of ground attack, Skitter away, and then do a different ground attack.

Grimm is one of the faster bosses in the game, and his health scales with nail upgrades, making him a tough foe regardless of experience or progress.

Because Grimm moves by way of teleportation and rarely stays in one place for long, from an offensive perspective, it's important to deal as much damage to Grimm in the shortest time possible.

Each spell has its use against Grimm. Vengeful Spirit is useful to use during the Cloak Spikes, Pufferfish Attacks and Fire Bats Attack. Desolate Dive is a great way to dodge the Dive Dash Attack. It's best to use it almost as soon as the player sees Grimm preparing the Dive Dash Attack because Grimm will land in the middle of it. Howling Wraiths can be useful during a Flamespawner Attack right before the fireballs start to spawn and during a Cloak Spikes Attack since Grimm is taller than the Knight.

The Nail Arts Great Slash and Dash Slash are also useful, providing 2.5x Nail damage and good range for damaging Grimm and staying safe (especially during Cloak Spikes, Dash Uppercut, and Fire Bats Attacks).

Use the Shade Cloak to dash through both of his Dash attacks (Dive Dash and Dash Uppercut). The player can also damage Grimm this way if they have Sharp Shadow.

Standing directly next to where Grimm explodes into fire when he uses Dash uppercut is a good way to avoid all 5 projectiles as they spread in a cone pattern, this also gives healing opportunity especially with Quick Focus.

During the Cloak Spikes attack, The player can use the time to heal. This is easier to do with Quick Focus.

Shape of Unn is a fantastic way to heal against Grimm. The charm lowers the Knight's hitbox so players can heal safely during a Fire Bats Attack. If combined with Quick Focus, the player can run and heal from Grimm during a Dash Uppercut Attack too. It can also be used to heal and position at the same time during the Cloak Spikes attack.

If the Knight stays near the the right/left side of the screen and light tap jumps, they can mostly avoid the flames during Grimm's Flamespawner Attack.

Double jump and dash over the Fire Bats, putting the Knight in range to attack.

It is possible to defeat Grimm under few seconds only Using Abyss Shriek in conjunction of Spell Twister, Shaman Stone & Stalwart Shell. While having all 3 Soul Vessels (Having Coiled Nail or higher, otherwise 2) fully filling them by Dream Nailing creatures from Forgotten Crossroads then when the fight starts hitting it while bowing to make it start his Flamespawner attack, quickly get under it and repeatedly using Abyss Shrieks. If the Knight does not have the required number of Soul Vessels, they can wear Grubsong to regain some soul by taking damage to use the final Attack. Using this won't let Grimm use any of its other attacks. According to the Nail upgrade, the number of uses varies:
 * Having Channeled Nail or lower upgrade, have to use 6 times.
 * Having Coiled Nail, have to use 7 times.
 * Having Pure Nail, have to use 8 times.



Trivia

 * Grimm always bows to the Knight before the start of the fight. If struck when bowing, he screeches at them and starts the Flamespawner attack.
 * When fought in Godhome, Grimm bows to the Godseeker instead of bowing to the Knight.


 * The Grimmchild charm is required every time to start the battle, except in Godhome.
 * Grimm is the only Boss to have music variations and audio cues for some events:
 * When Grimm performs the Flamespawner attack, the theme gets more dramatic by adding chorus to the background.
 * The Grimmkin audience watching gives an ovation to Grimm every time he performs the Flamespawner attack or reforms after stagger.
 * When Grimm reforms after stagger, he is accompanied by a drumroll.
 * Varying cues are also triggered during his fight in Godhome.
 * There is a secret area in Grimm's tent above the arena where the empty masks of the audience, some chests and a strange device can be found. It can be accessed by wall climbing through a false ceiling to the right of the arena, second arch.
 * When using a spell in this secret room some sort of barrier appears which may possibly be related to a Seal of Binding.
 * In a response to a question on Grimm's character inspirations in one of their Hollow Knight streams Team Cherry has stated:
 * Can you confirm Grimm was inspired by Dracula from Castlevania?

William: “He’s like a mix of a lot of things.” Ari: “Yeah, he has this kind of circus master quality, and-” ''William: “Halloween-y.. He’s spooky.”''
 * Ari: “I don’t think- I mean Grimm obviously has a lot of Dracula-like qualities. But he also has other elements.”


 * Even in Godhome, it is not possible to fight him alongside the Grimmchild. If equipped, it will not be present for the duration of the fight. The same is true for Nightmare King Grimm.

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