At the outset, the player-controlled insectoid warrior arrives in Dirtmouth, a quiet town that sits just above the remains of the kingdom of Hallownest. As the protagonist ventures through the ruins, they learn that Hallownest was once a flourishing kingdom of insects which fell after becoming overrun with "The Infection", a supernatural disease that can control the minds of bugs by entering the subject's dreams, driving them to madness and
undeath. Hallownest's ruler, The Pale King, had previously attempted to lock away the Infection in the Temple of the Black Egg. Despite the temple's magical seals, the disease managed to escape, and Hallownest fell into ruin. The protagonist's mission is to find and kill three bugs called the Dreamers, who act as the living seals on the temple door. Once the seals have been removed, the protagonist may confront the source of the Infection, the Radiance. The protagonist frequently encounters
Hornet, the daughter of the Pale King and one of the Dreamers, who tests the protagonist's combat prowess in two battles. Through dialogue with non-player characters, environmental imagery, and writings scattered throughout Hallownest, the protagonist learns the origins of the Infection. In ancient times, a tribe of moths that lived in Hallownest worshipped the Radiance, a primordial being who could control the minds of other bugs. When the Pale King arrived at Hallownest from afar, he used his powers to give sapience and knowledge to the creatures of the realm. The moths joined the bugs of Hallownest in worshipping the king, causing the Radiance to fall into obscurity. Beneath the notice of the Pale King, some worship of the Radiance continued, allowing her to remain alive inside the
Dream Realm. Hallownest prospered until the Radiance began appearing in the dreams of its people, poisoning their minds with the Infection. In an attempt to contain the Infection, the Pale King used a living substance called Void to create the Vessels, creatures made to contain the Infection within their own bodies. The Pale King chose the vessel most fit, the Hollow Knight, to trap the Radiance within itself, leaving the others locked in a pit called the Abyss. After the Hollow Knight was locked within the Temple of the Black Egg, the Radiance persisted within the Vessel, weakening the temple's seals and allowing the Infection to escape. Throughout the game, it is revealed that the protagonist was a Vessel who managed to escape the Abyss. They gradually defeat the Dreamers and their guardians, removing the seals on the door. Inside, they encounter and battle with the infected Hollow Knight. Depending on the player's actions, several endings can be achieved. These include the protagonist defeating the infected Hollow Knight and taking its place containing the Radiance, another where they defeat the Hollow Knight with Hornet's assistance, and a third where they fight and defeat the Radiance directly inside the Dream Realm.
The Grimm Troupe expansion In the second expansion to
Hollow Knight, a "Nightmare Lantern" was added to the Howling Cliffs area. After striking a masked bug with the Dream Nail, the lantern summons a mysterious group of circus performers to Dirtmouth, who identify themselves as the Grimm Troupe. Their leader, Troupe Master Grimm, gives the player a quest to collect magic flames throughout Hallownest in order to take part in a "twisted ritual", feeding off the nightmares of the dying kingdom to keep the Nightmare Heart alive. He gives the player the Grimmchild charm, which creates a small creature reminiscent of the Troupe Master when equipped; when it later absorbs the flames into itself, the ritual is progressed, and the Grimmchild gains the ability to attack the player's enemies. Eventually, the player must choose to either complete the ritual by fighting Grimm in his powerful Nightmare King form or prevent the ritual and banish the Grimm Troupe with the help of Brumm, a traitorous troupe member.
Godmaster expansion More content was added to
Hollow Knight with the fourth and final expansion,
Godmaster, in which the player unlocks a new area, Godhome, which includes several boss rushes, and "The Hall of Gods" a hallway of statues of the game's bosses, which, upon being selected, allow a rematch. The expansion focuses on the Godseekers, a tribe of bugs from a faraway land, abandoned by their gods. After obtaining the Godtuner, the knight can help the Godseekers atune to the gods of hallownest by completing five "pantheons", each containing a set of bosses that must all be defeated consecutively without dying. The final pantheon, the Pantheon of Hallownest, contains every boss in the game or alternate forms of original bosses. If the player completes the Pantheon of Hallownest, the Absolute Radiance, a more powerful version of the Radiance, appears, acting as the new final boss. Upon defeating her, two unique endings can be achieved in which the player morphs into a powerful Void entity and destroys Godhome. ==Development==