Hollow Knight

The Hollow Knight is the Vessel that was chosen by the Pale King to seal away the source of the Infection, the Radiance. Like all other Vessels, they have no gender. For more information on the purpose and backstory of Vessels see here.

Lore
They were described in the Birthplace memory as having no mind, no will, and no voice, which was necessary so that the Radiance would not be able to influence them. However, the White Lady mentions that the Hollow Knight's purity was ill-judged, and that they were "tarnished by an idea instilled". The events involving the Pale King shown in the Path of Pain and Birthplace scenes might have been contributing factors in this.

Regardless of their impurity, the Hollow Knight was trained and raised and eventually became a fully grown Vessel. They sealed the Radiance within themselves and were chained within the Temple of the Black Egg, where they were expected to contain the infection for eternity. However, because of the aforementioned impurities, the Radiance could still exert influence; ultimately resulting in the resurgence of the Infection and Hallownest falling into ruin.

Hollow Knight
After some time, the Radiance's power broke out of the Hollow Knight, cracking their shell and fully infecting them. This event was the catalyst that brought the Knight back to Hallownest. The Knight can fight the Hollow Knight after killing the three Dreamers who formed seals on the entrance to the Black Egg.

In two of the game's endings (the Hollow Knight and Sealed Siblings), the Knight kills the Hollow Knight, taking their place in sealing the Radiance. During the Dream No More ending, at the end of the fight with the Radiance, the Hollow Knight's Shade appears and opens up a weak point on her head, allowing the Knight to land the finishing blows. At the end of the Embrace the Void ending, the Hollow Knight is freed from the infection. They can be seen walking out of the Black Egg, where they are met by Hornet.

Behaviour and Tactics
The Hollow Knight will roar at the beginning of the fight, and once per every phase change.

Phase 1
These are the base attacks that The Hollow Knight starts with. These will be expanded on by the next 2 phases.

Phase 2
After reaching 750 hp The Hollow Knight gains these attacks in addition to the attacks of Phase 1. The Hollow Knight attacks and moves more frequently.

Phase 3
After reaching 400 hp The Hollow Knight gains these attacks in addition to the attacks from the previous phases, but however they lose the Lunge and Triple Slash attack. The Hollow Knight attacks and moves less frequently.

Phase 4
After reaching 0 hp The Hollow Knight will heal for 250 hp only if the fight is continued, but depending on the player's progress, the fight will be interrupted by Hornet, allowing The Knight to access their mind with the Dream Nail and fight The Radiance, otherwise the fight will continue as normal.

During the fourth phase of the battle, the Hollow Knight loses all other attacks except the Bouncing Balloon Attack and gains one new attack.

The Hollow Knight is one of two final bosses of the game.

Upon breaking the seals on the temple by destroying the three Dreamers, the player is allowed entrance in order to fight this boss. To begin the fight, the player must break the four chains holding the Hollow Knight.

The Hollow Knight fight happens over 4 Phases. Each Phase is marked by the Hollow Knight standing still, turning their head skyward and roaring. This roar stuns The Knight. The fight changes with each phase.

In Phase 1, the Hollow Knight has three attacks: Triple Slash, Lunge, and Parry. The attacks come regularly. The Hollow Knight will back dash, teleport, and leap around the arena between attacks.

In Phase 2 of the fight, the Hollow Knight gains two more attacks (Barrage and Diving Flame Pillar) and the Hollow Knight moves and attacks with greater frequency.

In Phase 3, the Hollow Knight begins stabbing themselves. The Hollow Knight gains two more attacks (Outbreak and Bouncing Balloon) but they also slow down: rarely leaping or teleporting and their attacks come less often.

In Phase 4, the Hollow Knight can barely move. They can no longer teleport or leap anymore and can hardly swing their Nail. Only two attacks are used in the phase: the Bouncing Balloon and Deterioration.

The main weakness of the Hollow Knight is that they are vulnerable to attacks from above. During a Lunge or Triple Slash, jump above their head and Nail bounce a few times while they finish the attack. If they try to Parry, dash away before they counter-attack.

There are safe zones amongst the blobs during the Barrage and Explosion Attacks so pay attention and move into safe zones. Dashing can often overshoot a safe zone, so walking is usually the safer option.

During the Bouncing Balloon Attack, the Hollow Knight will attempt to home in on the Knight. They will have trouble tracking if the player constantly changes direction. Dodge the first slam, then dash under them when they rise for a new slam, then reverse again after they come down and repeat.

During the Diving Flame Pillar Attack, the pillars will briefly charge on the floor before erupting, showing where it is safe to stand. When the Hollow Knight jumps and readies their Nail, start looking for a safe zone immediately after dodging the downward strike.

The Hollow Knight's teleport will usually position them far away from the player, so using Vengeful Spirit/Shade Soul during this time is useful to get hits in before they charge another attack. Moving too far from the Hollow Knight makes it more likely they will teleport close to the player, so be careful running away to heal.

Under normal circumstances, the Hollow Knight is immune to the Dream Nail and will not grant any SOUL on a successful hit.

Depending on the player's progress, one of two endings will play out after the fight. After the ending, the Knight will spawn at the last Bench rested at. The Hollow Knight can be dream nailed at the start of phase 4 if the player has the Void Heart, initiating the fight with The Radiance.

Trivia

 * The Hollow Knight can be found at a younger age during three other points within the game, during the Birthplace cutscene, the Path of Pain cutscene, and the Pantheon of the Knight cutscene.
 * It is uncertain as to why the Hollow Knight begins to stab themselves halfway through the fight. There are two distinct possibilities:
 * The Hollow Knight is able to take back some control from The Radiance and attempts to end their own life.
 * The Radiance makes the Hollow Knight stab themselves in order to be able to use more infection-based attacks.


 * The Hollow Knight fight is one of four fights in the game where an NPC aids the player; the other three are Traitor Lord with Cloth, Uumuu with Quirrel and The Radiance with the aid of The Hollow Knight.
 * The "idea instilled" which caused the impurity of the Hollow Knight may have been the father-child bond between The Pale King and the Hollow Knight, as is shown in a cutscene at the end of the Path of Pain. However, the Birthplace cutscene might imply that the Hollow Knight was impure from the moment they were born.
 * Even though their Shade has two arms, the Hollow Knight is never shown with a second arm during the battle.
 * Pure Vessel, the Hollow Knight's prime form, has both arms, suggesting that the Hollow Knight lost an arm after being infected.
 * The Hollow Knight, along with Pure Vessel, is the only boss whose title appears at the top-centre of the screen.
 * After the Knight absorbs the infection from The Hollow Knight, a bright silhouette of The Radiance can be seen for a split second as the Hollow Knight lets out their final roar before dying.
 * The Hollow Knight has cut Dream Nail dialogue which is the following:
 * ...Kill...
 * ...Shall blaze free...
 * ...This Vessel, broken...fails...
 * ...Dawn...Shall break...
 * ...No mind, the usurper...Only strength...
 * ...Kill the usurper...Our light it would suffocate...
 * ...Father?...