Pure Vessel

"Chosen vessel, raised and trained to prime form. "Deepest silence in holy shell, Given nail and named a Knight, Bound by chain and egg and spell, Hear Our plea! Reveal thy Light!""

- Prayer to the Vessel

The Pure Vessel is a quest boss in Hollow Knight introduced in Godmaster. They are the prime version of the Hollow Knight, unaffected by the Infection.

Behaviour and Tactics
Pure Vessel uses the following attacks:
 * Soul Daggers: Pure Vessel moves to either side of the arena, faces the Knight, and raises their hand. The hand glows white while they summon seven daggers that shoot towards the Knight in straight lines along an arc. The daggers are summoned sequentially: the first one firing at an angle towards the floor, and the last one firing straight up.
 * Triple Slash: Pure Vessel slashes with their Nail three times. Each slash of their Nail moves Pure Vessel forward, covering about 1/3 of the arena in total. The slashes cover enough space that they can damage the Knight even if they are not directly in front of Pure Vessel.
 * Soul Pillars: Pure Vessel either leaps or teleports into the air above where the Knight was and then slams into the ground, causing pillars of Soul to jut up from the floor of the arena. These pillars are equally spaced, allowing some safety between them, and they span the entire arena.
 * Lunge: Pure Vessel draws their Nail up and lunges along the ground towards the Knight. This lunge covers about 50% of the arena.
 * Parry: Pure Vessel takes up a defensive stance with their Nail. If the Knight damages them after their Nail shines, they will take no damage from the hit and instead will respond by shifting forward a little and slashing with their Nail.
 * Focus: Pure Vessel begins focusing Soul in a fashion similar to the Knight. However, unlike the Knight, Pure Vessel surrounds themselves with a circular aura that eventually explodes. Shortly after, six smaller auras appear randomly throughout the arena. Then these smaller auras explode in rapid succession in the order in which they appeared. Pure Vessel begins another attack as the final small explosion occurs. They start using this attack when they reach 1056 HP.
 * Void Tendrils: Pure Vessel opens their cloak, revealing several flailing void tendrils, including two larger ones. About three quarters of a second later, the two larger tendrils lash out across about 60% of the arena. The lashing continues for about three quarters of a second. They start using this attack when they reach 528 HP.
 * Jump: When the Knight has remained off the ground for too long, Pure Vessel will launch themselves at the Knight's location, dealing contact damage.
 * Teleport: Pure Vessel teleports within the arena to prepare for an attack or dodge the Knight.
 * Backstep: Pure Vessel will quickly backstep away from the Knight if they get too close and then perform another attack.

Pure Vessel's fight is a quick-paced fight. Pure Vessel chains attacks together without moving between them, backsteps between attacks, or teleport between attacks. It is recommended that players practice enough to recognize Pure Vessel's attacks quickly and be equally quick with their reactions.

Some options for handling the Triple Slash and Lunge: jumping over it, shadow dashing through it, or casting Descending Dark. Jumping over the Triple Slash requires either a well-timed Nail bounce or double jump (thanks to Monarch Wings) to avoid the second slash. Once the Knight past Pure Vessel, there can be an opportunity to damage them again before they attack again.

Once Pure Vessel is above the Knight for Soul Pillars, getting out of the way is most important, which can even mean using Descending Dark. Then the Knight needs to put themselves in between the Pillars, which can even mean Nail-bouncing on Pure Vessel. There is time to damage Pure Vessel while waiting for the Pillars to disappear.

The safest option when Pure Vessel gets into the Parry stance is to not attack them. Or the Knight can intentionally trigger the riposte and handle that.

When Pure Vessel prepares their Soul Daggers attack, there are telegraphed lines of travel showing the Knight the safe gaps between the Soul Daggers. The Knight can stay far away and cast Shade Soul or they can get in close and deal damage.

When Pure Vessel begins focusing, the Knight can stay far away and cast Shade Soul, stay close and get in some quick Nail damage before the explosion, or time Descending Dark to avoid the explosion. The first aura becomes dangerous shortly after the rocks float. After the initial explosion, it is important to deal damage while remaining safe from the follow-up explosions, which deal damage when they flash.

For Void Tendrils, it is most important to get out of the way, whether that is getting out of range, getting above, or getting behind Pure Vessel. When out of range, casting Shade Soul is a good option. When above, Nail-bouncing on Pure Vessel and/or casting Descending Dark is viable. Once behind, the Knight can do whatever they want while the attack occurs.

The Spell Abyss Shriek is most viable when Pure Vessel is staggered due to how long it takes to cast. Even then, Pure Vessel could exit stagger into a Parry and Abyss Shriek could trigger the riposte so be aware.

The safest time to heal is when Pure Vessel is staggered. Without charms, the Knight can heal 1 mask safely or maybe 2 if they start healing as soon as Pure Vessel is staggered. The Knight can heal 1 mask during Soul Pillars if they start healing before the Pillars form and Pure Vessel takes a moment before attacking again; when Pure Vessel Focuses (or 2 masks if a smaller explosion does not spawn on the the Knight); during Soul Daggers if the Knight is already in a safe position; during a parry if the the Knight predicts it; and when the Knight is out of range of Void Tendrils.

Quick Focus helps but generally does not provide enough time to get another mask during these no-charm moments but does grant more time to safely react to Pure Vessel. The Knight can eke out a third mask when Pure Vessel is staggered. Adding Shape of Unn to Quick Focus grants the Knight enough maneuverability to safely heal 1 or more masks during all of these moments.

NOTE: The Dream Nail and Flukenest do not work or have an effect against Pure Vessel. Edit: Flukenest only works when Pure Vessel is in the air. Tested using Debugmod.

Trivia

 * The Pure Vessel was shown through the trailer of Godmaster to be fully armoured, however, this armour is only displayed for a couple of seconds at the beginning of the Pure Vessel fight before being ripped off.
 * Pure Vessel, along with the Hollow Knight, is the only boss whose title appears at the top of the screen.
 * Unlike the Hollow Knight, Pure Vessel's pre-battle cry is silent.
 * In the release, Pure Vessel cannot be Dream Nailed, but has the following cut Dream Nail dialogue:
 * Do not think...
 * Do not speak...
 * Do not hope...
 * Do not...

References

Чистый Сосуд Reines Gefäß Ricettacolo Puro Nieskalany Vessel